UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

Commission file number 1-4682

Thomas & Betts Corporation

(Exact name of registrant as specified in its charter)

(901) 252-8000

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act: None

     Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.    Yes x    No o

     Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K. o

     Indicate by check mark whether the registrant is an accelerated filer (as defined in Exchange Act Rule 12b-2). Yes x    No o

     As of June 30, 2004, the last business day of the registrant’s most recently completed second fiscal quarter, the aggregate market value of the voting and non-voting common equity held by non-affiliates (based on the closing price on the New York Stock Exchange as of such date) was $1,597,406,506.

     As of March 1, 2005, 59,576,721 shares of the Registrant’s common stock were outstanding.

Documents Incorporated by Reference

     Portions of the definitive Proxy Statement for the Annual Meeting of Shareholders will be filed within 120 days after the end of the fiscal year covered by this report and are incorporated by reference into Part III.

Thomas & Betts Corporation and Subsidiaries

TABLE OF CONTENTS

CAUTION REGARDING FORWARD-LOOKING STATEMENTS

      This Report includes forward-looking statements regarding Thomas & Betts Corporation that are subject to uncertainties in our operations, business, economic and political environment. Statements that contain words such as “achieve,” “guidance,” “believes,” “expects,” “anticipates,” “intends,” “estimates,” “continue,” “should,” “could,” “may,” “plan,” “project,” “predict,” “will” or similar expressions are forward-looking statements. These statements are subject to risks and uncertainties, and many factors could affect our future financial condition or results of operations. Accordingly, actual results, performance or achievements may differ materially from those expressed or implied by the forward-looking statements contained in this Report. We undertake no obligation to revise any forward-looking statement included in the Report to reflect any future events or circumstances. For more information regarding our risks, please see Item 7. Management’s Discussion and Analysis of Financial Condition and Results of Operations — Business Risks. Reference in this Report to “we,” “our,” “us,” “Thomas & Betts” or “the Corporation” refers to Thomas & Betts Corporation and its consolidated subsidiaries.

PART I

      Thomas & Betts Corporation is a leading designer and manufacturer of electrical connectors and components used in industrial, commercial, communications, and utility markets. We are also a leading producer of commercial heating units and highly engineered steel structures used for, among other things, utility transmission. We operate approximately 120 manufacturing, distribution and office facilities around the world in approximately 20 countries. Manufacturing, marketing and sales activities are concentrated primarily in North America and Europe. We pursue growth through market penetration, new product development, and, at times, acquisitions.

      We sell our products

      Thomas & Betts was first established in 1898 as a sales agency for electrical wires and raceways, and was incorporated and began manufacturing products in New Jersey in 1917. We were reincorporated in Tennessee in 1996. Our corporate offices are maintained at 8155 T&B Boulevard, Memphis, Tennessee 38125, and the telephone number at that address is 901-252-8000.

Available Information

      Our internet address is www.TNB.com. We will make available free of charge on our Internet website, our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and amendments to those reports as soon as reasonably practicable after they are electronically filed with, or furnished to, the Securities and Exchange Commission (“SEC”). We will provide electronic or paper copies of our filings free of charge upon request.

General Segment Information

      We classify our products into the following business segments based primarily on product lines. Our segments are:

      The majority of our products, especially those sold in the Electrical segment, have region-specific product standards and are sold mostly in North America or in other regions sharing North American electrical codes. No customer accounted for 10% or more of our consolidated net sales for 2004, 2003, or 2002.

Electrical Segment

      Our Electrical segment’s markets include industrial, commercial, utility and residential construction, renovation, maintenance and repair; project construction; industrial original equipment manufacturers; and communications. The segment’s sales are concentrated primarily

in North America and Europe. The Electrical segment experiences modest seasonal increases in sales during the second and third quarters reflecting the construction season. Net sales for the Electrical segment for the past three years were:

      The Electrical segment designs, manufactures and markets thousands of different connectors, components and other products for electrical, utility and communications applications. We have a market-leading position for many of our products. Products in the Electrical segment include:

      These products are sold under a variety of well-known brand names, such as Color Keyed®, Elastimold®, Kindorf®, Red Dot®, Sta-Kon®, Steel City®, Superstrut®, Ty-Rap®, LRC®, Diamond®, Kold-N-Klose® and Snap-N-Seal®.

      Demand for electrical products follows general economic conditions and is sensitive to activity in construction markets, industrial production levels and spending by utilities for replacements, expansions and efficiency improvements. The segment’s product lines are predominantly sold through major distributor chains, thousands of independent distributors and, to a lesser extent, to retail home centers and hardware outlets. They are also sold directly to original equipment manufacturers, utilities, cable operators, and telecommunications and satellite TV companies. We have strong relationships with our distributors as a result of the breadth and quality of our product lines, our market-leading service programs, our strong history of product innovation, and the high degree of brand-name recognition for our products among end-users.

Steel Structures Segment

      Our Steel Structures segment designs, manufactures and markets highly engineered tubular steel transmission and distribution poles and lattice steel transmission towers for North American power and telecommunications companies. These products are primarily sold to the following types of end-users:

      These products are marketed primarily under the Meyer® and Thomas & Betts® brand names. Net sales for the Steel Structures segment for the past three years were:

HVAC Segment

      Our HVAC segment designs, manufactures and markets heating and ventilation products for commercial and industrial buildings. Products in this segment include:

      These products are sold primarily under the Reznor® brand name through HVAC, mechanical and refrigeration distributors throughout North America and Europe. Demand for HVAC products tends to be higher when customers are experiencing cold weather and, as a result, HVAC has higher sales in the first and fourth quarters. To reduce the impact of seasonality on operations, the segment offers an off-season promotional program with its distributors. Net sales for the HVAC segment for the past three years were:

Manufacturing and Distribution

      We employ advanced processes for manufacturing quality products. Our manufacturing processes include high-speed stamping, precision molding, machining, plating and automated assembly. We make extensive use of computer-aided design and computer-aided manufacturing (CAD/ CAM) software and equipment to link product engineering with our manufacturing facilities. We also utilize other advanced equipment and techniques in the manufacturing and

distribution process, including computer software for scheduling, material requirements planning, shop floor control, capacity planning, and the warehousing and shipment of products.

      Our products have historically enjoyed a reputation for quality in the markets in which they are sold. To ensure maintenance of our quality standards, all of our facilities embrace quality programs, and as of December 31, 2004, approximately 55% meet the ISO 9001 2000 standard. Additionally, we have implemented quality control processes in our design, manufacturing, delivery and other operations in order to further improve product quality and customer service levels.

Raw Materials

      We purchase a wide variety of raw materials for the manufacture of our products including steel, aluminum, zinc, copper, resins and rubber compounds. Sources for raw materials and component parts are well established and, with the exception of steel, are sufficiently numerous to avoid serious future interruptions of production in the event that current suppliers are unable to provide raw materials and component parts sufficient to meet our needs. However, our industry has experienced a reduction in the number of steel suppliers during the past two years due to consolidation. Given the current tight supply of steel, we could encounter manufacturing disruptions in each of our segments from sporadic interruptions by our steel suppliers. In addition, we could encounter price increases, especially for steel, that we may not be able to pass on to our customers.

Research and Development

      We have research, development and engineering capabilities in each business segment and maintain facilities that respond to the needs of specific markets. We have a long-term reputation for innovation and value based upon our ability to develop products that meet the needs of the marketplace.

      Research, development and engineering expenditures invested into new and improved products and processes are shown below. These expenses are included in cost of sales in the Consolidated Statements of Operations.

Working Capital Practices

      We maintain sufficient inventory to enable us to provide a high level of service to our customers. Our inventory levels, payment terms and return policies are in accordance with general practices associated with the industries in which we operate.

Patents and Trademarks

      We own approximately 1,300 active patent registrations and applications worldwide. We have over 1,400 active trademarks and domain names worldwide, including: Thomas & Betts, T&B, T&B Access, Blackburn, Bowers, Canstrut, Catamount, Color-Keyed, Commander, Deltec, Diamond, DuraGard, Elastimold, Emergi-Lite, E-Z-Code, Flex-Cuf, Furse, Hazlux, Kindorf, Klik-It, Kold-N-Klose, LRC, Marr, Marrette, Meyer, Ocal, Red Dot, Reznor, Russellstoll, Sachs,

Shamrock, Shield-Kon, Shrink-Kon, Signature Service, Site Light, Snap-N-Seal, Sta-Kon, Star Teck, Steel City, Superstrut, Taylor, Ty-Fast, Ty-Rap and Union.

      While we consider our patents, trademarks, and trade dress to be valuable assets, we do not believe that our competitive position is dependent solely on patent or trademark protection or that any business segment or our operations as a whole is dependent on any individual patent or trademark. However, the Color-Keyed, Elastimold, Kindorf, Red Dot, Sta-Kon, Steel City, Super-Strut,and Ty-Rap trademarks are important to the Electrical segment; the Meyer trademark is important to the Steel Structures segment; and the Reznor trademark is important to the HVAC segment. In addition, we do not consider any of our individual licenses, franchises or concessions to be material to our business as a whole or to any business segment.

Competition

      Our ability to continue to meet customer needs by enhancing existing products and developing and manufacturing new products is critical to our prominence in our primary market, the electrical products industry. We have robust competition in all areas of our business, and the methods and levels of competition, such as price, service, warranty and product performance, vary among our markets. While no single company competes with us in all of our product lines, various companies compete with us in one or more product lines. Some of these competitors have substantially greater sales and assets and greater access to capital than we do. We believe Thomas & Betts is among the industry leaders in service to its customers.

      We continually work to enhance our product offerings as do our competitors who are likely to develop new offerings with competitive price and performance characteristics. Although we believe that we have specific technological and other advantages over some of our competitors, because of the intensity of competition in the product areas and geographic markets that we serve, we could experience increased downward pressure on the selling prices for some of our products.

      The abilities of our competitors to enhance their own products, coupled with any unforeseeable changes in customer demand for various products of Thomas & Betts, could affect our overall product mix, pricing, margins, plant utilization levels and asset valuations. We believe that industry consolidation could further increase competitive pressures.

Employees

      As of December 31, 2004, we had approximately 9,000 full-time employees worldwide. Employees of our foreign subsidiaries in the aggregate comprise approximately 50% of all employees. Of the total number of employees, approximately one-third are represented by trade unions. We believe our relationships with our employees and trade unions are good.

Compliance with Environmental Regulations

      We are subject to federal, state, local and foreign environmental laws and regulations that govern the discharge of pollutants into the air, soil and water, as well as the handling and disposal of solid and hazardous wastes. We believe that we are in compliance, in all material respects, with applicable environmental laws and regulations and that the costs of maintaining such compliance with applicable environmental laws and regulations will not be material to our financial position or results of operations.

Financial Information About Foreign and U.S. Operations

      Export sales originating in the U.S. were approximately $34 million in 2004, $33 million in 2003, and $44 million in 2002. For additional financial information about international and U.S. operations, please refer to Note 16 in the Notes to Consolidated Financial Statements.

      As of December 31, 2004, we had approximately 120 plant, office, distribution, storage and warehouse facilities, occupying approximately 6.8 million sq. ft. in 21 U.S. states, the Commonwealth of Puerto Rico and in approximately 20 other countries. This space is comprised of approximately 4.7 million sq. ft. of manufacturing space; 1.8 million sq. ft. of office, distribution, storage and warehouse space; and 0.3 million sq. ft. of idle space.

      Our manufacturing locations by segment as of December 31, 2004, were as follows:

      In addition to the above manufacturing facilities, we own three central distribution centers located in Belgium (0.1 million sq. ft.), Canada (0.3 million sq. ft.) and Byhalia, Mississippi (0.9 million sq. ft.). We also have principal sales offices, warehouses and storage facilities

located in approximately 0.5 million sq. ft. of space, most of which is leased. Included in this total is approximately 0.2 million sq. ft. of leased space in Memphis, Tennessee, which includes our corporate headquarters.

Kaiser Litigation

      By July 5, 2000, Kaiser Aluminum, its property insurers, 28 Kaiser injured workers, nearby businesses and a class of 18,000 residents near the Kaiser facility in Louisiana, filed product liability and business interruption cases against the Corporation and six other defendants in Louisiana state court seeking damages in excess of $550 million. These cases alleged that a Thomas & Betts cable tie mounting base failed thereby allowing bundled cables to come in contact with a 13.8 kv energized bus bar. This alleged electrical fault supposedly initiated a series of events culminating in an explosion, which leveled 600 acres of the Kaiser facility.

      A seven-week trial in the fall 2001 resulted in a jury verdict in favor of the Corporation. However, 13 months later, the trial court overturned that verdict in granting plaintiffs’ judgment notwithstanding the verdict motions. On December 17, 2002, the trial court judge found the Thomas & Betts’ product, an adhesive backed mounting base, to be unreasonably dangerous and therefore assigned 25% fault to T&B. The judge set the damages for an injured worker at $20 million and the damages for Kaiser at $335 million. The judgment did not address damages for nearby businesses or 18,000 residents near the Kaiser facility. The Corporation’s 25% allocation is $88.8 million, plus legal interest. The Corporation has appealed this ruling. Management believes there are meritorious defenses to the claim and intends to contest the litigation vigorously.

      The appeal required a bond in the amount of $104 million (the judgment plus legal interest). Plaintiffs successfully moved the trial court to increase the bond to $156 million. The Corporation’s liability insurers have secured the $156 million bond.

      The Corporation has not reflected a liability in its financial statements for the Kaiser litigation because management believes meritorious defenses exist for this claim and thus management does not believe a loss is probable. Further, until there are new developments in the case that would provide more definitive amounts, management cannot provide any better range of possible losses than zero to the amount of the judgment. When evaluating the impact of the judgment on the Corporation’s liquidity, investors should note that the Corporation has insurance coverage in excess of the judgment.

      The nearby businesses have made demands for unspecified damages, but to date, no discovery has taken place.

      In the fourth quarter 2004, the Corporation and the class of 18,000 residents reached settlement for claims by the class members. The settlement extinguishes the claims of all class members and includes indemnity of the Corporation against future potential claims asserted by class members or those class members who opted out of the settlement process. Also in the fourth quarter 2004, the court approved the class settlement at a fairness hearing. The $3.75 million class settlement amount has been paid directly by an insurer of the Corporation into a trust for the benefit of class members.

Asbestos Cases

      The Corporation and two subsidiaries, Amerace Corporation and L.E. Mason (Red Dot), acquired respectively in 1995 and 1999, are subject to asbestos lawsuits in Mississippi, New Jersey and four other states, related to either undefined and unidentified or historic products. In all cases, the Corporation is investigating these allegations. Amerace is one of hundreds of defendants and Red Dot and the Corporation are one of dozens of defendants in each case. No asbestos containing product of Amerace, Red Dot or Thomas & Betts has been identified in these cases to date. In the Amerace cases, ten lawsuits have already been dismissed. Potential exposure at this time, if any, cannot be estimated. Management believes, however, that there is no merit to these claims, that damages, if any, are remote and believes that a loss is not probable in any of these cases. Insurance coverage is available in connection with these claims.

Other Legal Matters

      The Corporation is also involved in legal proceedings and litigation arising in the ordinary course of business. In those cases where we are the defendant, plaintiffs may seek to recover large and sometimes unspecified amounts or other types of relief and some matters may remain unresolved for several years. Such matters may be subject to many uncertainties and outcomes which are not predictable with assurance. We consider the gross probable liability when determining whether to accrue for a loss contingency for a legal matter. We have provided for losses to the extent probable and estimable. The legal matters that have been recorded in our consolidated financial statements are based on gross assessments of expected settlement or expected outcome. Additional losses, even though not anticipated, could have a material adverse effect on our financial position, results of operations or liquidity in any given period.

Environmental Matters

      Owners and operators of sites containing hazardous substances, as well as generators of hazardous substances, are subject to broad and retroactive liability for investigatory and cleanup costs and damages arising out of past disposal activities. Such liability in many cases may be imposed regardless of fault or the legality of the original disposal activity. We have been notified by the United States Environmental Protection Agency or similar state environmental regulatory agencies or private parties that we, in many instances along with others, may currently be potentially responsible for the remediation of sites pursuant to the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended, similar federal and state environmental statutes, or common law theories. We, along with others, may be held jointly and severally liable for all costs relating to investigation and remediation of 12 sites pursuant to these environmental laws.

      We are the owner or operator, or former owner or operator, of various manufacturing locations that we are currently evaluating for the presence of contamination that may require remediation. These sites include former or inactive facilities or properties in Alabama (Mobile); Connecticut (Monroe); Indiana (Medora); Illinois (Libertyville); Massachusetts (Attleboro, Boston, Canton); New Hampshire (New Milford); New Jersey (Butler, Elizabeth, Garwood); New York (Horseheads); Pennsylvania (Perkasie, Pittsburgh); Ohio (Bucyrus) and Oklahoma (Stillwater). The sites further include active manufacturing locations in New Jersey (Hackettstown); New Mexico (Albuquerque); South Carolina (Lancaster); and Wisconsin (Hager City).

      Four of these current and former manufacturing locations relate to activities of American Electric for the period prior to our acquisition of that company. These four sites are located in

Hager City, Wisconsin, Lancaster, South Carolina, Medora, Indiana, and Pittsburgh, Pennsylvania. Each of these sites, except for Pittsburgh is subject to an Asset Purchase Agreement dated June 28, 1985 between American Electric and ITT Corporation. ITT and Thomas & Betts have shared responsibilities and costs at the four outstanding sites subject to this agreement. For certain of the sites covered by this agreement, ITT agreed to indemnify American Electric for environmental liabilities, if any, that occurred prior to the purchase of the facilities by American Electric. We believe that the indemnity of ITT is reliable; however, we have no assurances that these indemnities will be honored.

      In 1996, we acquired Augat Inc. Augat previously evaluated or remediated, and may have liability associated with environmental contamination at a number of sites. Pursuant to a Purchase Agreement, dated July 2, 2000, between the Corporation and Tyco Group S.A.R.L., we agreed to retain certain environmental liabilities, if any, for former Augat manufacturing locations in Alabama (Montgomery Plants 1 & 3); Massachusetts (Mashpee) and South Carolina (Inman); and for four offsite alleged disposal locations.

      In November 1998, we acquired Kaufel Group, Ltd. Pursuant to the various environmental laws and regulations described above, we are evaluating, and may have liability associated with contamination at two facilities owned and operated by Kaufel in Dorval, Quebec.

      We have provided for liabilities to the extent probable and estimable, but we are not able to predict the extent of our ultimate liability with respect to all of these pending or future environmental matters. However, we believe that any additional liability with respect to the aforementioned environmental matters will not be material to our financial position or results of operations.

      No matters were submitted to a vote of security holders during the fourth quarter of the fiscal year ended December 31, 2004.

Executive Officers

      The following persons are executive officers of Thomas & Betts, and are elected by and serve at the discretion of the Board of Directors.

Dominic J. Pileggi, 53

President & Chief Executive Officer

      Mr. Pileggi was elected Chief Executive Officer in January 2004. Mr. Pileggi has held several executive positions with the company, including President and Chief Operating Officer from 2003 to 2004, and Senior Vice President and Group President — Electrical from 2000 to 2003. He also held various executive positions with Thomas & Betts from 1979 to 1995. Mr. Pileggi was employed by Viasystems Group, Inc., as Executive Vice President in 1998 to 2000 and President — EMS Division of Viasystems in 2000.

Kenneth W. Fluke, 45

Senior Vice President & Chief Financial Officer

      Mr. Fluke was elected Senior Vice President and Chief Financial Officer effective May 2004. Prior to that time, he was Vice President — Controller from 2000. Previously, he held various finance and managerial positions with The Goodyear Tire and Rubber Company

beginning in 1982, including General Manager, Finance — South Pacific Tyres and Controller North American Tires Division.

Christopher P. Hartmann, 43

President — Electrical Division

      Mr. Hartmann has been President — Electrical Division since 2003 and was elected an executive officer effective May 2004. Prior to that time, he was President and Chief Operating Officer of Affiliated Distributors, North America’s largest network of independent electrical distributors from 1999 to 2002.

Connie C. Muscarella, 50

Vice President — Human Resources and Administration

      Ms. Muscarella has been Vice President — Human Resources since 1999 and has served as the elected officer position of Vice President — Human Resources and Administration since 2000.

J.N. Raines, 61

Vice President–General Counsel & Secretary

      Mr. Raines was elected to the officer position of Vice President — General Counsel & Secretary in 2001. Prior to that time, he was a partner of the law firm of Glankler Brown PLLC for more than five years.

NYSE Certifications

      Our CEO certified to the New York Stock Exchange in 2004 that we were in compliance with the NYSE listing standards. In 2004, our CEO and CFO executed the certification required by section 302 of the Sarbanes-Oxley Act of 2002, which was an exhibit to our Form 10-K for the fiscal year ended December 31, 2003.

PART II

Market Information

      Our common stock is traded on the New York Stock Exchange under the symbol TNB. The following table sets forth by quarter for the last two years the high and low sales prices of our common stock as reported by the NYSE.

      At March 1, 2005, the closing price of the Corporation’s common stock on the NYSE was $32.73.

Holders

      At March 1, 2005, the Corporation had approximately 3,300 shareholders of record, not including shares held in security position listings, or “street name.”

Dividends

      We do not presently anticipate declaring any cash dividends in the foreseeable future. Future decisions concerning the payment of cash dividends will depend upon our results of operations, financial condition, capital expenditure plans, terms of credit agreements, and other factors that the Board of Directors may consider relevant. The 7.25% notes due 2013 contain provisions that currently limit the amount of cash dividends that Thomas & Betts is allowed to pay.

Thomas & Betts Corporation and Subsidiaries

Executive Overview

Introduction