Exhibit 99.1

FOR IMMEDIATE RELEASE

DATE: October 23, 2013

HERITAGE FINANCIAL ANNOUNCES THIRD

QUARTER RESULTS AND DECLARES REGULAR

CASH DIVIDEND

Olympia, WA—HERITAGE FINANCIAL CORPORATION (NASDAQ GS: HFWA) Brian L. Vance, President and CEO of Heritage Financial Corporation (“Company” or “Heritage”), today reported that the Company had net income of $3.3 million for the quarter ended September 30, 2013 compared to net income of $2.9 million for the quarter ended September 30, 2012 and $2.7 million for the linked-quarter ended June 30, 2013. Net income for the quarter ended September 30, 2013 was $0.20 per diluted common share compared to $0.19 per diluted common share for the quarter ended September 30, 2012 and $0.18 per diluted common share for the linked-quarter ended June 30, 2013.

Net income for the nine months ended September 30, 2013 was $8.9 million, or $0.57 per diluted common share, compared to $10.2 million, or $0.67 per diluted common share, for the nine months ended September 30, 2012.

Mr. Vance commented, “We are beginning to see the tangible results from our acquisitions of Northwest Commercial Bank and Valley Bank and the merger of our Central Valley Bank subsidiary into Heritage Bank. We also successfully completed a significant upgrade to our core operating system over the first weekend of October that will give us efficiency gains and a better foundation to support growth.” Mr. Vance continued, “Our capital ratios continue to be very strong and we feel that we are in a good position to grow organically and to continue to be able to take advantage of acquisition opportunities that we believe still exists.”

Acquisition of Northwest Commercial Bank

On January 9, 2013, the Company acquired Northwest Commercial Bank (“NCB”) and merged it into Heritage Bank (“NCB Acquisition”). NCB was a full service commercial bank with branches in Lakewood and Auburn, Washington. In March 2013, the Company consolidated the operations of the former NCB Lakewood branch with the Lakewood branch of Heritage Bank.

The Company paid cash consideration of $3.0 million, or $5.50 per share, to the NCB shareholders. Additionally, as provided for in the merger agreement, NCB shareholders had the ability to potentially receive an additional cash payment based on an earn-out structure from the sale of an other real estate owned asset of NCB. This contingent

payment was included in the NCB liabilities assumed as of the January 9, 2013 acquisition date. During the quarter ended June 30, 2013 this asset was sold and the $491,000 in proceeds from the sale was paid to the former NCB shareholders. This payment did not impact the recorded bargain purchase gain on bank acquisition.

In connection with the NCB Acquisition, the Company received (at fair value) approximately $51.5 million in loans, $2.7 million of cash and cash equivalents, $2.8 million in investment securities, $2.9 million in net deferred tax assets, $2.3 million in other real estate owned, $1.0 million of other interest earning deposits and $1.9 million in other assets. The Company also assumed deposits with a fair value of approximately $60.4 million and $1.2 million of other liabilities. The application of the acquisition method of accounting resulted in the recognition of a pre-tax bargain purchase gain on bank acquisition of $399,000. The bargain purchase gain on bank acquisition represents the excess of the estimated fair value of the net assets acquired and the liabilities assumed over the purchase price.

During the three and nine months ended September 30, 2013, the Company incurred NCB Acquisition-related costs (including conversion costs) of approximately $5,000 and $746,000, respectively.

Central Valley Bank Merger

On June 19, 2013, the Company completed the merger of its subsidiary, Central Valley Bank (“CVB”), with and into Heritage Bank (the “CVB Merger”). CVB is now operated as a division of Heritage Bank. During the three and nine months ended September 30, 2013, the Company incurred CVB Merger-related costs of approximately $6,000 and $129,000, respectively.

Acquisition of Valley Community Bancshares

On July 15, 2013, the Company completed the acquisition of Valley Community Bancshares, Inc. (“Valley”), the holding company for Valley Bank, both of Puyallup, Washington (the “Valley Acquisition”). Pursuant to the terms of the merger agreement, Valley shareholders received for each share of Valley common stock $19.50 in cash and 1.3611 shares of Heritage common stock. As of the acquisition date, Valley merged into Heritage and Valley Bank merged into Heritage Bank.

In connection with the Valley Acquisition, the Company received (at fair value) approximately $117.1 million in loans, $40.6 million of cash and cash equivalents, $13.9 million of other interest earning deposits, $54.4 million in investment securities, $7.0 million in premises and equipment, $916,000 in core deposit intangible and $3.5 million in other assets. The Company also assumed deposits with a fair value of approximately $207.0 million and $342,000 of other liabilities. The application of the acquisition method of accounting resulted in the recognition of goodwill of $16.4 million. The goodwill represents the excess of the consideration transferred over the estimated fair value of the net assets acquired and the liabilities assumed.

During the three and nine months ended September 30, 2013, the Company incurred Valley Acquisition-related costs of approximately $161,000 and $515,000, respectively.

Balance Sheet

The Company’s total assets increased to $1.67 billion at September 30, 2013 from $1.43 billion at June 30, 2013. The increase in total assets from the prior period was primarily due to the assets acquired in the Valley Acquisition.

Total originated loans receivable increased $29.4 million to $961.9 million at September 30, 2013 from $932.5 million at June 30, 2013. The increase from the prior period was due primarily to increases in commercial and industrial loans ($8.6 million), owner-occupied commercial real estate loans ($9.5 million) and non-owner occupied commercial real estate loans ($10.4 million).

Total deposits increased to $1.43 billion at September 30, 2013 from $1.20 billion at June 30, 2013. The increase was primarily due to the deposits acquired in the Valley Acquisition. Non-maturity deposits to total deposits increased to 77.6% at September 30, 2013 from 76.1% at June 30, 2013. In addition, noninterest demand deposits to total deposits increased to 25.4% at September 30, 2013 from 22.9% at June 30, 2013.

Total stockholders’ equity increased to $216.6 million at September 30, 2013 from $200.5 million at June 30, 2013. The increase during the three months ended September 30, 2013 was primarily due to the issuance of 1.53 million shares of Heritage common stock of $24.2 million in the Valley Acquisition, $3.3 million in net income and $229,000 in stock-based compensation, which were partially offset by $8.6 million in stock repurchases, $3.0 million in cash dividends and an increase of $173,000 in accumulated other comprehensive loss, net. During the

quarter ended September 30, 2013, the Company repurchased 544,490 shares at a weighted average price per share of $15.88. The Company’s ratio of tangible common equity to tangible assets decreased to 11.3% at September 30, 2013 from 13.2% at June 30, 2013. The Company and Heritage Bank continue to maintain capital levels significantly in excess of the applicable regulatory requirements for them to be categorized as “well-capitalized”. The Company had Tier 1 leverage, Tier 1 risk-based and total risk-based capital ratios at September 30, 2013 of 11.6%, 15.5% and 16.7%, respectively, as compared to 13.1%, 17.5%, and 18.8%, at June 30, 2013, respectively.

Credit Quality

The allowance for loan losses on originated loans decreased $465,000 to $17.4 million at September 30, 2013 from $17.8 million at June 30, 2013 as a result of $615,000 in net charge-offs recognized during the quarter ended September 30, 2013 partially offset by $150,000 in provision for loan losses. Nonperforming originated loans to total originated loans decreased to 0.81% at September 30, 2013 from 1.05% at June 30, 2013. Nonaccrual originated loans decreased $2.0 million to $9.8 million ($7.9 million net of government agency guarantees) at September 30, 2013 from $11.7 million ($9.7 million net of government agency guarantees) at June 30, 2013. The decrease in nonaccrual originated loans was due to $1.8 million of net principal reductions and $477,000 of charge-offs partially offset by an addition of one loan in the amount of $315,000 to nonaccrual originated loans.

The allowance for loan losses to nonperforming originated loans was 221.68% at September 30, 2013 compared to 182.81% at June 30, 2013. Potential problem originated loans decreased to $26.6 million at September 30, 2013 from $29.2 million at June 30, 2013. Restructured originated performing loans increased slightly to $19.6 million at September 30, 2013 compared to $19.4 million at June 30, 2013. The Company believes that its allowance for loan losses is appropriate to provide for probable incurred losses based on an evaluation of known and inherent risks in the loan portfolio at September 30, 2013.

Nonperforming originated assets were $13.6 million ($11.7 million net of government agency guarantees), or 0.83% of total originated assets, at September 30, 2013, compared to $15.2 million ($13.2 million net of government agency guarantees), or 1.06% of total originated assets, at June 30, 2013. Other real estate owned increased $333,000 to $4.1 million at September 30, 2013 from $3.8 million at June 30, 2013 (at both dates $317,000 was covered by FDIC loss sharing agreements). The increase was due primarily to the addition of three properties totaling $1.2 million partially offset by the disposition of four properties totaling $849,000. During the quarter ended September 30, 2013, the Company recognized a net gain of $75,000 on the disposition of other real estate owned and a negative valuation adjustment of $45,000.

Mr. Vance added, “The credit quality of our originated loan portfolio continues to improve. Our loan loss allowance coverage ratio is a very strong 222% of nonperforming originated loans, excluding portions guaranteed by government agencies. As credit quality continues to improve, our ratio of the allowance for loan losses on originated loans to total originated loans is likely to continue to decrease. At the end of the third quarter our allowance for loan losses on originated loans remains a very healthy 1.80%.”

Operating Results

Net interest income increased $1.6 million, or 10.2%, to $17.6 million for the quarter ended September 30, 2013 compared to $16.0 million for the same period in 2012. Net interest income increased $1.2 million, or 2.5%, to $50.1 million for the nine months ended September 30, 2013 compared to $48.9 million for the same period in 2012. The increases in net interest income are due to increases in average interest earning assets (substantially attributable to the NCB Acquisition and the Valley Acquisition) partially offset by declines in the net interest margin (substantially due to lower contractual loan note rates).

Heritage’s net interest margin for the quarter ended September 30, 2013 decreased 42 basis points to 4.67% from 5.09% for the same period in 2012 and decreased 15 basis points from 4.82% in the linked-quarter ended June 30, 2013. The declines in net interest margin are due primarily to lower contractual loan note rates. Heritage’s net interest margin for the nine months ended September 30, 2013 decreased 35 basis points to 4.88% from 5.23% for the same period in 2012.

The positive effect on the net interest margin of discount accretion on the acquired loan portfolios for the quarter ended September 30, 2013 was approximately 38 basis points compared to 49 basis points in the same quarter of the prior year and 45 basis points for the linked-quarter ended June 30, 2013. Interest reversals on nonaccrual originated loans reduced the net interest margin for the quarter ended September 30, 2013 by approximately four basis points compared to six basis points for the same quarter in the prior year and five basis points for the linked-quarter ended June 30, 2013.

The positive effect on the net interest margin of discount accretion on the acquired loan portfolios was 51 basis points for both the nine months ended September 30, 2013 and September 30, 2012. Interest reversals on nonaccrual originated loans reduced the net interest margin for the nine months ended September 30, 2013 by five basis points compared to seven basis points for the same period in the prior year.

The provision for loan losses on originated loans was $150,000 for the quarter ended September 30, 2013 compared to $215,000 for the quarter ended September 30, 2012 and $345,000 for the linked-quarter ended June 30, 2013. For the nine months ended September 30, 2013, the provision for loan losses on originated loans was $990,000 compared to $415,000 for the same period in the prior year. The Company had net charge-offs on originated loans of $615,000 for the quarter ended September 30, 2013 compared to $525,000 for the quarter ended September 30, 2012 and $435,000 for the linked-quarter ended June 30, 2013. For the nine months ended September 30, 2013, the Company had net charge-offs on originated loans of $2.8 million compared to $2.2 million for the same period in the prior year.

The provision for loan losses on purchased loans totaled $928,000 for the quarter ended September 30, 2013 compared to $592,000 for the same period in the prior year and $963,000 for the linked-quarter ended June 30, 2013. For the nine months ended September 30, 2013, the provision for loan losses on purchased loans was $2.3 million compared to $902,000 for the same period in the prior year.

As of the acquisition dates, purchased loans were recorded at their estimated fair values, incorporating our estimate of future expected cash flows until the ultimate resolution of these credits. To the extent actual or projected cash flows are less than previously estimated, additional provisions for loan losses on the purchased loan portfolios are recognized immediately into earnings. To the extent actual or projected cash flows are more than previously estimated, the increase in cash flows is recognized immediately as a recapture of provision for loan losses up to the amount of any provision previously recognized for that pool of loans, if any, then prospectively recognized in interest income as a yield adjustment.

Cash flows on pools of acquired loans are re-estimated on a quarterly basis. As reflected in the table below, incremental accretion income was $1.4 million for the quarter ended September 30, 2013 compared to $1.5 million for the linked-quarter ended June 30, 2013. For the nine months ended September 30, 2013, incremental accretion income was $5.2 million compared to $4.8 million for the same period in the prior year.

For the quarter ended September 30, 2013, the Company recognized $(350,000) of change in the FDIC indemnification asset compared to $281,000 and $(492,000) for the quarters ended June 30, 2013 and September 30, 2012, respectively. The decrease for the quarter ended September 30, 2013 as compared to the quarter ended June, 30, 2013 was primarily due to a collateral valuation adjustment of a large purchased covered loan during the quarter ended June 30, 2013 which resulted in an addition to the FDIC indemnification asset.

The following table illustrates the significant accounting entries associated with the Company’s acquired loan portfolios:

Donald J. Hinson, Executive Vice President and Chief Financial Officer, commented, “Our net interest margin continues to experience compression due to the current low rate environment. The net interest margin before incremental accretion income decreased 8 basis points to 4.29% for the quarter ended September 30, 2013 compared to 4.37% for the linked-quarter ended June 30, 2013. This decrease was driven by lower contractual yields on the loan portfolio. Loan yields before incremental accretion income decreased 12 basis points to 5.35% for the quarter ended September 30, 2013 compared to 5.47% for the linked-quarter ended June 30, 2013. This compression is expected to continue as the average rates on new loans are lower than the current average yield of the loan portfolio.”

Noninterest income was $2.6 million for the quarter ended September 30, 2013 compared to $1.5 million for the same period in 2012 and $2.4 million for the linked-quarter ended June 30, 2013. The increase in the quarter ended September 30, 2013 from the same period in the prior year was primarily due to a $596,000 gain on the sale of a branch building (included in “other income”) which occurred in August 2013 and an increase of $212,000 in service charges and other fees. The branch building was sold in connection with the relocation of the branch to a more favorable location. The increase from the linked-quarter ended June 30, 2013 was partially offset by a decrease of $631,000 in income due to the change in FDIC indemnification asset.

For the nine months ended September 30, 2013, noninterest income was $7.2 million compared to $5.5 million for the nine months ended September 30, 2012. The increase was primarily due to the previously mentioned gain on sale of a branch building, a $399,000 pre-tax bargain purchase gain on bank acquisition recognized during the first quarter of 2013 on the NCB Acquisition, an increase of $278,000 in service charges and other fees and a $351,000 improvement to income from the change in FDIC indemnification asset.

Noninterest expense was $14.3 million for the quarter ended September 30, 2013 compared to $12.5 million for the quarter ended September 30, 2012 and $13.0 million for the linked-quarter ended June 30, 2013. The $1.3 million increase for the quarter ended September 30, 2013 compared to the linked-quarter ended June 30, 2013 was primarily due to the addition of Valley operating expenses as well as acquisition and core system conversion related expenses.

Noninterest expense increased $3.0 million to $41.0 million for the nine months ended September 30, 2013 from $38.0 million for the nine months ended September 30, 2012. The increase was primarily due to the addition of operating expenses of NCB and Valley and approximately $1.8 million of costs related to mergers/acquisitions and costs incurred related to the core system conversion which was completed in October 2013.

Income tax expense was $1.5 million for the quarter ended September 30, 2013 compared to $1.3 million for the comparable quarter in 2012 and $1.3 million for the linked-quarter ended June 30, 2013. The increase in income tax expense for the quarter ended September 30, 2013 from the prior periods was primarily due to the increase in pre-tax income.

Dividend

On October 23, 2013, the Company’s Board of Directors declared a quarterly cash dividend of $0.08 per common share payable on November 15, 2013 to shareholders of record on November 5, 2013.

Earnings Conference Call

The Company will hold a telephone conference call to discuss this earnings release on October 24, 2013 at 9:00 a.m. Pacific time. To access the call, please dial (800) 288-8961 a few minutes prior to 9:00 a.m., Pacific time. The call will be available for replay through November 7, 2013, by dialing (800) 475-6701 — access code 304998. This is a change in the date and phone number from the previous earnings conference call announcement.

About Heritage Financial

Heritage Financial Corporation is an Olympia-based bank holding company with Heritage Bank, a full-service commercial bank, as its wholly-owned banking subsidiary. Following the CVB merger and the merger with Valley Bank, Heritage Bank now has forty-two banking offices in Washington and Oregon. Heritage Bank does business under the Central Valley Bank name in the Yakima and Kittitas counties of Washington. The Company’s stock is traded on the NASDAQ Global Select Market under the symbol “HFWA”. More information about Heritage Financial Corporation can be found on its website at www.hf-wa.com and more information about Heritage Bank can be found on its website at www.heritagebanknw.com.

Contact:

Brian L. Vance, President & Chief Executive Officer, (360) 943-1500

Donald J. Hinson, Executive Vice President & Chief Financial Officer, (360) 943-1500

Non-GAAP Financial Measures

This news release contains certain non-GAAP financial measures in addition to results presented in accordance with Generally Accepted Accounting Principles (GAAP). These measures include tangible common equity, tangible book value per share and tangible common equity to tangible assets. Tangible common equity (tangible book value) excludes goodwill and other intangible assets. Tangible assets exclude goodwill and other intangible assets. Management has presented these non-GAAP financial measures in this earnings release because it believes that they provide useful and comparative information to assess trends in the Company’s capital reflected in the current quarter and year-to-date results. Where applicable, the Company has also presented comparable capital information using GAAP financial measures. Reconciliations of the GAAP and non-GAAP financial measures are presented below.

Forward-Looking Statements

“Safe Harbor” statement under the Private Securities Litigation Reform Act of 1995: This release contains forward-looking statements that are subject to risks and uncertainties, including, but not limited to: the credit risks of lending activities, including changes in the level and trend of loan delinquencies and write-offs and changes in our allowance for loan losses and provision for loan losses that may be impacted by deterioration in the housing and commercial real estate markets; changes in general economic conditions, either nationally or in our market areas; changes in the levels of general interest rates, and the relative differences between short and long term interest rates, deposit interest rates, our net interest margin and funding sources; fluctuations in the demand for loans, the number of unsold homes and other properties and fluctuations in real estate values in our market areas; results of examinations of us by the Board of Governors of the Federal Reserve System and of our bank subsidiary by the Federal Deposit Insurance Corporation, the Washington State Department of Financial Institutions, Division of Banks or other regulatory authorities, including the possibility that any such regulatory authority may, among other things, require us to increase our allowance for loan losses, write-down assets, change our regulatory capital position or affect our ability to borrow funds or maintain or increase deposits, or impose additional requirements and restrictions on us, any of which could adversely affect our liquidity and earnings; legislative or regulatory changes that adversely affect our business including changes in regulatory policies and principles, including the interpretation of regulatory capital or other rules including changes related to Basel III; the impact of the Dodd-Frank Wall Street Reform and Consumer Protection Act and the implementing of regulations; our ability to control operating costs and expenses; the use of estimates in determining the fair value of certain of our assets, which estimates may prove to be incorrect and result in significant declines in valuation; difficulties in reducing risk associated with the loans on our balance sheet; staffing fluctuations in response to product demand or the implementation of corporate strategies that affect our workforce and potential associated charges; computer systems on which we depend could fail or experience a security breach; our ability to retain key members of our senior management team; costs and effects of litigation, including settlements and judgments; our ability to implement our expansion strategy; our ability to successfully integrate any assets, liabilities, customers, systems, and management personnel we have acquired including the Cowlitz Bank, Pierce Commercial Bank, Northwest Commercial Bank and Valley Community Bancshares transactions, or may in the future acquire into our operations, and our ability to realize related revenue synergies and cost savings within expected time frames and any goodwill charges related thereto; risks relating to acquiring assets or entering markets in which we have not previously

operated and may not be familiar; changes in consumer spending, borrowing and savings habits; the availability of resources to address changes in laws, rules, or regulations or to respond to regulatory actions; adverse changes in the securities markets; inability of key third-party providers to perform their obligations to us; changes in accounting policies and practices, as may be adopted by the financial institution regulatory agencies or the Financial Accounting Standards Board, including additional guidance and interpretation on accounting issues and details of the implementation of new accounting methods; other economic, competitive, governmental, regulatory, and technological factors affecting our operations, pricing, products and services; and other risks detailed from time to time in our filings with the Securities and Exchange Commission.

The Company cautions readers not to place undue reliance on any forward-looking statements. Moreover, you should treat these statements as speaking only as of the date they are made and based only on information then actually known to the Company. The Company does not undertake and specifically disclaims any obligation to revise any forward-looking statements to reflect the occurrence of anticipated or unanticipated events or circumstances after the date of such statements. These risks could cause our actual results for future periods to differ materially from those expressed in any forward-looking statements by, or on behalf of, us, and could negatively affect the Company’s operating and stock price performance.

HERITAGE FINANCIAL CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION

(Dollar amounts in thousands; unaudited)

HERITAGE FINANCIAL CORPORATION

CONDENSED CONSOLIDATED STATEMENTS OF INCOME

(Dollar amounts in thousands, except per share amounts; unaudited)

HERITAGE FINANCIAL CORPORATION

FINANCIAL STATISTICS

(Dollar amounts in thousands; unaudited)

HERITAGE FINANCIAL CORPORATION

FINANCIAL STATISTICS

(Dollar amounts in thousands; unaudited)

HERITAGE FINANCIAL CORPORATION

FINANCIAL STATISTICS

(Dollar amounts in thousands, except per share amounts; unaudited)

HERITAGE FINANCIAL CORPORATION

FINANCIAL STATISTICS

(Dollar amounts in thousands; unaudited)