Exhibit 99.1

FOR IMMEDIATE RELEASE

F5 Networks Announces Fourth Quarter and Fiscal 2012 Results

Fourth quarter revenue up 15 percent year over year; 2012 revenue up 20 percent from 2011

SEATTLE, WA—October 24, 2012—F5 Networks, Inc. (NASDAQ: FFIV) today announced revenue of $362.6 million for the fourth quarter of fiscal year 2012, up 3 percent from $352.6 million in the prior quarter and 15 percent from $314.6 million in the fourth quarter of fiscal year 2011. For fiscal year 2012, revenue was $1.38 billion, up 20 percent from $1.15 billion in fiscal year 2011.

GAAP net income for the fourth quarter was $67.7 million ($0.85 per diluted share) compared to $72.3 million ($0.91 per diluted share) in the third quarter of 2012 and $67.6 million ($0.84 per diluted share) in the fourth quarter a year ago. GAAP net income for the year was $275.2 million ($3.45 per diluted share) versus $241.4 million ($2.96 per diluted share) in fiscal year 2011.

Excluding the impact of stock-based compensation and amortization of purchased intangible assets, non-GAAP net income for the fourth quarter was $88.7 million ($1.12 per diluted share), compared to $90.6 million ($1.14 per diluted share) in the prior quarter and $85.2 million ($1.06 per diluted share) in the fourth quarter of fiscal 2011. For fiscal year 2012, non-GAAP net income was $348.6 million ($4.37 per diluted share) versus $308.3 million ($3.78 per diluted share) in fiscal year 2011.

The company’s GAAP and non-GAAP net income reflect higher than expected effective tax rates for fiscal year 2012. This resulted from a higher than expected impact of foreign permanent tax differences and a higher blended effective state tax rate which resulted in a GAAP effective tax rate for the fourth quarter of 39.9 percent. The non-GAAP effective tax rate for the quarter was 37.0 percent.

A reconciliation of GAAP net income to non-GAAP net income is included on the attached Consolidated Statements of Operations.

“F5 grew sequentially and year over year throughout fiscal 2012,” said F5 president and chief executive officer John McAdam. “But after a strong first half, revenue growth slowed in the second half of the year. Beginning in the third quarter and continuing through Q4, slowing growth in product revenue reflected smaller deal sizes, particularly among large U.S. enterprise and telecommunications customers. Annual U.S. revenue grew just over 16 percent from fiscal 2011. By contrast, international revenue grew nearly 24 percent in fiscal 2012, resulting in overall revenue growth of 20 percent for the year.

“We maintained strong product gross margins for the quarter and the year at 83 percent and as a result, we were able to add 540 employees in fiscal 2012, including 125 in Q4, while delivering a non-GAAP operating margin of 39 percent,” said McAdam.

During the fourth quarter, the company increased deferred revenue by $13.4 million to $447.3 million, up 30 percent from the fourth quarter of fiscal 2011. Cash flow from operations was $149 million in the fourth quarter and $495 million for the year. After repurchasing approximately 1.7 million shares of F5 common stock during fiscal 2012, the company ended the year with $1.2 billion in cash and investments.

“As we enter fiscal 2013, it is difficult to predict what turns the economy will take. But as we look out over the year, we believe that changes in the evolving technology landscape are creating new opportunities for growth and that our technology roadmap and product deliverables will enable us to capitalize on those changes. On October 16, 2012 we introduced BIG-IP 4200v, the first in a series of new appliances that will replace our entry-level and mid-range BIG-IP platforms and extend our market leadership in price/performance and functionality. In addition to these new platforms, we will be introducing significant performance and functionality enhancements to TMOS and new software modules that will expand the array of integrated application delivery functions currently available on our platforms and in virtual editions. We will also expand and upgrade our VIPRION family of chassis products over the next several quarters.

“While we are excited about these new products and their potential to drive revenue growth, current macroeconomic conditions and our expectation of normal Q1 seasonality have tempered our outlook for the near term,” said McAdam.

For the first quarter of fiscal 2013, ending December 31, the company has set a revenue target of $363 million to $370 million with a GAAP earnings target of $0.86 to $0.88 per diluted share. Excluding stock-based compensation expense and amortization of purchased intangible assets, the company’s non-GAAP earnings target is $1.14 to $1.16 per diluted share.

A reconciliation of the company’s expected GAAP and non-GAAP earnings is provided in the following table:

Analyst/Investor Meeting

F5 will hold a meeting for analysts and investors at The Roosevelt Hotel in New York City, from 8:00 a.m. to 12:30pm Eastern Time on Thursday, November 15, 2012.

To register online, please visit: https://www.f5.com/about/investor-relations/analyst-meeting/

For more information contact Darlene Henderson (206.272.6170) or email 2012AIM@f5.com.

The meeting will also be webcast live and an archived version will be available through January 23, 2013. The link for the live webcast and the archived version is http://www.f5.com/about/investor-relations/events-calendar.html.

About F5 Networks

F5 Networks, Inc., the global leader in Application Delivery Networking (ADN), helps the world’s largest enterprises and service providers realize the full value of virtualization, cloud computing, and on-demand IT. F5^® solutions help integrate disparate technologies to provide greater control of the infrastructure, improve application delivery and data management, and give users seamless, secure, and accelerated access to applications from their corporate desktops and smart devices. An open architectural framework enables F5 customers to apply business policies at “strategic points of control” across the IT infrastructure and into the public cloud. F5 products give customers the agility they need to align IT with changing business conditions, deploy scalable solutions on demand, and manage mobile access to data and services. Enterprises, service and cloud providers, and leading online companies worldwide rely on F5 to optimize their IT investments and drive business forward. For more information, go to www.f5.com.

You can also follow @f5networks on Twitter or visit us on Facebook for more information about F5, its partners, and technology. For a complete listing of F5 community sites, please visit www.f5.com/news-press-events/web-media/community.html.

Forward Looking Statements

Statements in this press release concerning the continuing strength of F5’s business, sequential growth, the target revenue and earnings range, share amount and share price assumptions, demand for application delivery networking and storage virtualization products and other statements that are not historical facts are forward-looking statements. Such forward-looking statements involve risks and uncertainties, as well as assumptions and other factors that, if they do not fully materialize or prove correct, could cause the actual results, performance or achievements of the company, or industry results, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors include, but are not limited to: customer acceptance of our new traffic management, security, application delivery, WAN optimization and storage virtualization offerings; the timely development, introduction and acceptance of additional new products and features by F5 or its competitors; competitive pricing pressures; increased sales discounts; uncertain global economic conditions which may result in reduced customer demand for our products and services and changes in customer payment patterns; F5’s ability to sustain, develop and effectively utilize distribution relationships; F5’s ability to attract, train and retain qualified product development, marketing, sales, professional services and customer support personnel; F5’s ability to expand in international markets; the unpredictability of F5’s sales cycle; the share repurchase program; future prices of F5’s common stock; and other risks and uncertainties described more fully in our documents filed with or furnished to the Securities and Exchange Commission. All forward-looking statements in this press release are based on information available as of the date hereof and qualified in their entirety by this cautionary statement. F5 assumes no obligation to revise or update these forward-looking statements.

Use of non-GAAP Financial Information

F5’s management evaluates and makes operating decisions using various operating measures. These measures are generally based on the revenues of its products, services operations and certain costs of those operations, such as cost of revenues, research and development, sales and marketing and general and administrative expenses. One such measure is net income excluding stock-based compensation, amortization of purchased intangible assets and acquisition-related charges, net of taxes, which is a non-GAAP financial measure under Section 101 of Regulation G under the Securities Exchange Act of 1934, as amended. This measure consists of GAAP net income excluding, as applicable, stock-based compensation, amortization of purchased intangible assets and acquisition-related charges. This measure of non-GAAP net income is adjusted by the amount of additional taxes or tax benefit that the company would accrue if it used non-GAAP results instead of GAAP results to calculate the company’s tax liability. Stock-based compensation is a non-cash expense that F5 has accounted for since July 1, 2005 in accordance with the fair value recognition provisions of Financial

Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) Topic 718 Compensation—Stock Compensation (“FASB ASC Topic 718”). Amortization of intangible assets is a non-cash expense. Investors should note that the use of intangible assets contribute to revenues earned during the periods presented and will contribute to revenues in future periods. Acquisition-related expenses consist of professional services fees incurred in connection with acquisitions.

Management believes that non-GAAP net income per share provides useful supplemental information to management and investors regarding the performance of the company’s core business operations and facilitates comparisons to the company’s historical operating results. Although F5’s management finds this non-GAAP measure to be useful in evaluating the performance of the core business, management’s reliance on this measure is limited because items excluded from such measures could have a material effect on F5’s earnings and earnings per share calculated in accordance with GAAP. Therefore, F5’s management will use its non-GAAP earnings and earnings per share measures, in conjunction with GAAP earnings and earnings per share measures, to address these limitations when evaluating the performance of the company’s core business. Investors should consider these non-GAAP measures in addition to, and not as a substitute for, financial performance measures in accordance with GAAP.

F5 believes that presenting its non-GAAP measure of earnings and earnings per share provides investors with an additional tool for evaluating the performance of the company’s core business and which management uses in its own evaluation of the company’s performance. Investors are encouraged to look at GAAP results as the best measure of financial performance. However, while the GAAP results are more complete, the company provides investors this supplemental measure since, with reconciliation to GAAP, it may provide additional insight into the company’s operational performance and financial results.

For reconciliation of this non-GAAP financial measure to the most directly comparable GAAP financial measure, please see the section in our Condensed Consolidated Statement of Operations entitled “GAAP to Non-GAAP Reconciliation.”

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F5 Networks, Inc.

Consolidated Balance Sheets

(unaudited, in thousands)

F5 Networks, Inc.

Consolidated Statements of Operations

(unaudited, in thousands, except per share amounts)

F5 Networks, Inc.

Consolidated Statements of Cash Flows

(unaudited, in thousands)