UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K/A

For the fiscal year ended September 30, 2011

For the transition period from            to             .

Commission file number: 001-32469

XENONICS HOLDINGS, INC.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (760) 477-8900

Securities registered pursuant to Section 12(b) of the Act: Common Stock, $.001 par value

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

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.    ¨  Yes    þ  No

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or 15(d) of the Exchange Act.    ¨  Yes    þ  No

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.     þ  Yes    ¨  No

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). þ Yes ¨ No

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 the 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.    þ

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer,” and “smaller reporting company” in Rule 12b-2 of the Exchange Act (Check one):

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act):    ¨  Yes    þ  No

The aggregate market value of the common stock held by non-affiliates of the registrant as of March 31, 2011 (the last business day of the registrant’s most recently completed second fiscal quarter) was approximately $11,240,000.

There were 24,975,929 shares of the registrant’s common stock outstanding on January 24, 2012.

EXPLANATORY NOTE

The purpose of this amendment is to include the information required by Part III of Form 10-K, which was omitted from the Company’s Form 10-K as originally filed on December 19, 2011. Except as otherwise expressly set forth in this amendment, no portion of the Form 10-K filed on December 19, 2011 is being amended or updated by this amendment and this amendment does not reflect events that occurred after December 19, 2011.

1

PART III

ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE

Executive Officers and Directors

The directors and executive officers of the Company are as follows:

Directors are elected at each annual meeting of shareholders, and each executive officer serves until his resignation, death, or removal by the Board of Directors.

Alan P. Magerman. Mr. Magerman, age 76, founded Xenonics, Inc. in November 1996, and has been Chairman of Xenonics Holdings, Inc. since its acquisition of Xenonics, Inc. in July 2003. He served as Chief Executive Officer of Xenonics Holdings, Inc. from July 2003 through April 2005 and has served as our Chief Executive Officer from February 2009 to the present. Prior to founding Xenonics, Mr. Magerman was a founder and former chairman of Odyssey Sports, Inc., a privately held company engaged in the development and distribution of golf clubs from 1990 through 1995. Mr. Magerman was a consultant and director of NTN Communications, Inc. (NTN), a publicly held broadcasting and cable television company, from 1984 through 1997.

Mr. Magerman’s diverse business experience provides him with a wide range of expertise that is valuable to the Board of Directors in confronting various business-related challenges and opportunities.

Jeffrey P. Kennedy. Mr. Kennedy, age 57, has been a director and the President and Chief Operating Officer of Xenonics, Inc. since June 1997. Mr. Kennedy has held the same positions with Xenonics Holdings, Inc. since the acquisition of Xenonics, Inc. in July 2003. Prior to joining Xenonics, Inc., Mr. Kennedy held a variety of management positions with Mobil Corporation, including General Manager of the Mobil Chemical Plastics Division. He was educated at the University of Maine, receiving a BS degree in chemistry and an MS degree in chemical engineering.

As our President and Chief Operating Officer, Mr. Kennedy has extensive knowledge about the Company which provides a valuable resource for the Board of Directors in connection with its decisions about the operations and future direction of the Company.

Richard S. Kay. Mr.Kay, age 69, joined Xenonics in May 2007 and has been the Chief Financial Officer, Secretary and Treasurer of Xenonics, Inc. since then. From February 2001 through October 2006 he held the position of Chief Executive Officer of Pacer Technology. Mr. Kay graduated from the University of Wisconsin – Milwaukee with a BBA and majored in Accounting and Military Science. Early in his career he worked as a CPA in Wisconsin and California.

Allen K. Fox. Mr. Fox, age 75, has been managing personal finances and providing consulting work for several public companies since 1995, and was elected as a director of the Company on July 1, 2010. Mr. Fox has also served as a director and/or officer for several charitable organizations during the last 40 years. He

2

co-founded Odyssey Sports Co. in 1990 and was a director and an officer of that company. The company was sold in 1995. Mr. Fox also co-founded NYSE education company, Career Com, Corp. in 1969. He was a director and officer and sold his interest in 1989. From 1960 to 1969 he was a partner with an accounting firm. Mr. Fox graduated from Temple University in 1958.

Mr. Fox brings to the Board extensive experience in serving as an officer and a director of, and as a consultant to, numerous public and private companies. Mr. Fox’s experience as a partner of an accounting firm also assists the Board in addressing accounting requirements with which the Company must comply.

Brad J. Shapiro. Mr. Shapiro, age 57, has been a principal in various businesses in the optical industry since 1990. He is currently a principal in C & E Vision Services, Inc, and Vision West, Inc., which together comprise the largest optical group purchasing organizations in the United States. He is also principal, co-founder and co-Chief Executive Officer of Rudy Project North America, L.P., the exclusive North American distributor of Rudy Project sport eyewear. From 1989 to 1990, Mr. Shapiro was a Managing Director of an investment-banking subsidiary of Cantor Fitzgerald and another investment banking firm. For seven years prior to that time, Mr. Shapiro was a corporate and securities lawyer at Skadden, Arps, Slate, Meagher & Flom, an international law firm, and certain other law firms. Mr. Shapiro has served as a director of the Company since July 1, 2010. Mr. Shapiro holds a B.A. in Political Science from the University of Michigan and received his J.D. degree from the University of Michigan Law School in December 1990.

Mr. Shapiro brings to the Board a diversified business and legal background that is valuable in analyzing various business related challenges and opportunities.

Code of Ethics

We have adopted a Code of Business Conduct and Ethics that applies to our principal executive officer, principal financial officer, and principal accounting officer or controller. You can obtain a copy of the Code, without charge, by writing to our Corporate Secretary at Xenonics Holdings, Inc., 3186 Lionshead Avenue, Suite 100, Carlsbad, California 92010. A copy of the Code is also available on our website at www.xenonics.com.

Audit Committee

The Audit Committee assists the Board of Directors in fulfilling its oversight responsibilities relating to:

The Audit Committee appoints the independent registered public accounting firm, reviews with the independent registered public accounting firm the plans and results of the audit engagement, approves permitted non-audit services provided by our independent registered public accounting firm, and reviews the independence of the independent registered public accounting firm. The members of the Audit

3

Committee are Messrs. Fox and Shapiro, each of whom is “independent” under the independence standards of both the NYSE Amex and the Securities and Exchange Commission (the “SEC”). The Board of Directors has determined that Mr. Fox is an “audit committee financial expert” as defined by the rules of the SEC. The Audit Committee’s Charter is on our website at www.xenonics.com.

Compensation Committee

The Compensation Committee is authorized to review and make recommendations to the full Board of Directors relating to the annual salaries and bonuses of our officers and to determine in its sole discretion all grants of stock options, the exercise price of each option, and the number of shares to be issuable upon the exercise of each option under our stock option plans. The Committee also is authorized to interpret our stock option plans, to prescribe, amend and rescind rules and regulations relating to the plans, to determine the term and provisions of the respective option agreements, and to make all other determinations deemed necessary or advisable for the administration of the plans. The Compensation Committee’s Charter is on our website at www.xenonics.com. The members of the Compensation Committee are Messrs. Fox and Shapiro.

Nominating and Governance Committee

The Nominating and Governance Committee assists our Board of Directors in discharging its duties relating to corporate governance and the compensation and evaluation of the Board. The purpose of the Committee is to (1) identify individuals who are qualified to become members of the Board, consistent with criteria approved by the Board, (2) select, or recommend for the Board’s selection, the director nominees for each annual meeting of shareholders, (3) develop and recommend to the Board a set of corporate governance principles applicable to Xenonics, (4) oversee the annual evaluation of the Board and management, and (5) perform such other actions within the scope of the Committee’s Charter as the Committee deems necessary or advisable. A copy of the Nominating and Governance Committee’s Charter is available on our website at www.xenonics.com. The members of the Nominating and Governance Committee are Messrs. Fox and Shapiro.

The Nominating and Governance Committee has not established any specific minimum qualifications for director candidates or any specific qualities or skills that a candidate must possess in order to be considered qualified to be nominated as a director. Qualifications for consideration as a director nominee may vary according to the particular areas of expertise being sought as a complement to the existing Board composition. In making its nominations, our Nominating and Governance Committee generally will consider, among other things, an individual’s business experience, industry experience, financial background, breadth of knowledge about issues affecting our company, time available for meetings and consultation regarding company matters and other particular skills and experience possessed by the individual. Although the Nominating and Governance Committee believes that director nominees should add to the range of backgrounds and experiences of the Company’s directors, neither the Nominating and Governance Committee nor the Board of Directors has a policy regarding the consideration of diversity in identifying and evaluating director nominees.

Section 16(a) Beneficial Ownership Reporting Compliance

Section 16(a) of the Securities Exchange Act of 1934 requires our directors and executive officers, and persons who own more than 10% of the outstanding shares of our common stock (collectively, “Reporting Persons”) to file reports of ownership and changes in ownership with the SEC. Reporting Persons are required by SEC regulations to furnish us with copies of all Section 16(a) forms that they file.

Based solely on our review of the copies of such forms received or written representations from the Reporting Persons, we believe that, with respect to the fiscal year ended September 30, 2011, all of the Reporting Persons complied with all applicable Section 16 filing requirements on a timely basis.

4

ITEM 11. EXECUTIVE COMPENSATION

Executive Compensation

The following table sets forth the compensation for the fiscal years ended September 30, 2011 and September 30, 2010 for services rendered to us (including our subsidiary, Xenonics, Inc.) by our Chief Executive Officer and our two most highly compensated executive officers other than our Chief Executive Officer:

Summary Compensation Table

Compensation of Directors

When Allen K. Fox and Brad J. Shapiro became directors on July 1, 2010, we agreed to compensate all non-employee directors for their services. We issued to each of Mr. Fox and Mr. Shapiro a stock option to purchase 20,000 shares of our common stock at an exercise price of $0.65 per share, which vested immediately. We also agreed to pay each non-employee director $5,000 as an annual director’s fee, $500 for each committee meeting attended (if such committee meeting was not held in conjunction with a Board meeting), and $1,000 for each meeting of the Board of Directors attended. These fees are paid on a quarterly basis.

5

In addition, as Chairman of the Audit Committee Mr. Fox receives a monthly fee of $2,000 and, as Chairman of the Corporate Development Committee, he receives a monthly fee of $5,000.

The following table sets forth information concerning the compensation paid to our non-employee directors during our fiscal year ended September 30, 2011 for their services rendered as directors.

DIRECTOR COMPENSATION FOR FISCAL YEAR 2011

Stock Option Grants

The following table sets forth information as of September 30, 2011 concerning unexercised options, unvested stock and equity incentive plan awards for each of the executive officers named in the Summary Compensation Table.

OUTSTANDING EQUITY AWARDS AT YEAR ENDED SEPTEMBER 30, 2011

6

Employment Agreements

Alan P. Magerman and Jeffrey P. Kennedy are our only employees who have employment agreements. Under his employment agreement, Mr. Magerman is to serve as the Chief Executive Officer of Xenonics, Inc., and Mr. Kennedy is to serve as President and Chief Operating Officer of Xenonics, Inc. Both employment agreements were entered into by Xenonics, Inc. as of January 1, 2003 and, as amended, are substantially identical. Neither employment agreement has a fixed term or expiration date. On December 15, 2010, the Board of Directors approved an amendment to each agreement to provide that either party can terminate the agreement with 30 days written notice. However, in the event of termination by Xenonics without cause, the former officer’s right to receive his base salary will continue for 36 months after the notice of termination. Both agreements provide for base compensation of $180,000 per year, to be adjusted annually according to the Consumer Price Index.

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT AND RELATED STOCKHOLDER MATTERS

Security Ownership of Certain Beneficial Owners and Management

The following table sets forth certain information regarding the beneficial ownership of our common stock as of January 24, 2012 by (1) each person who is known by us to own beneficially more than five percent of our outstanding common stock, (2) each of our current directors and director nominees, (3) the executive officers listed above in the Summary Compensation Table, and (4) all current executive officers and directors as a group. The number of shares and the percentage of shares beneficially owned by each such person or group, as set forth below, include shares of common stock that such person or group had the right to acquire on or within sixty days after January 24, 2012 pursuant to the exercise of vested and exercisable options or warrants. References to options or warrants in the footnotes to the table below include only options or warrants to purchase shares that were exercisable on or within sixty days after January 24, 2012.

7

Equity Compensation Plan Information

The following table provides information as of September 30, 2011 with respect to securities that may be issued under our equity compensation plans.

8

The equity compensation plans approved by the security holders are the 2003 Stock Option Plan of Xenonics Holdings, Inc. and the 2004 Stock Incentive Plan of Xenonics Holdings, Inc. Except as described in the following paragraph, the Company had not adopted as of September 30, 2011, without the approval of security holders, any equity compensation plan under which securities of the issuer are authorized for issuance.

On November 11, 2009 the Company entered into an agreement with an independent firm to conduct institutional investor services for a period of one year. As part of this agreement the Company issued a five-year warrant, vested upon issuance, to purchase 100,000 shares of the Company’s common stock at $0.50 per share.

9

ITEM 13. CERTAIN RELATIONSHIPS AND RELATED TRANSACTIONS, AND DIRECTOR INDEPENDENCE

The Board of Directors has determined that directors Allen K. Fox and Brad J. Shapiro are each “independent” under the independence standards of both the NYSE Amex and the SEC.

During the year ended September 30, 2011, Bryant Park Capital, whose Managing Partner and CEO is Alan P. Magerman’s son, billed the Company $80,000 for investment banking services rendered to the Company.

ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES

Aggregate fees billed to us by SingerLewak LLP with respect to our 2011 and 2010 fiscal years were as follows:

In the above table, in accordance with the SEC’s definitions and rules, “audit fees” are fees that Xenonics Holdings, Inc. paid for professional services for the audit of our consolidated financial statements included in our Form 10-K and for services that are normally provided by the registered public accounting firm in connection with statutory and regulatory filings or engagements; “audit-related fees” are fees for assurance and related services that are reasonably related to the performance of the audit or review of our financial statements; and “tax fees” are fees for tax compliance, tax advice and tax planning.

All of the audit-related services and other services described in the above table were pre-approved by our Audit Committee. The Audit Committee has adopted a pre-approval policy that provides for the pre-approval of all services performed for us by SingerLewak LLP. The policy authorizes the Audit Committee to delegate to one or more of its members pre-approval authority with respect to permitted services. Pursuant to this policy, the Audit Committee delegated such authority to the Chairman of the Audit Committee. All pre-approval decisions must be reported to the Audit Committee at its next meeting.

10

PART IV

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES

11

12

13

SIGNATURES

Pursuant to the requirements of Section 13 or 15(d) of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.

14