Exhibit 99.1

News Release

ACI Worldwide, Inc. Reports Financial

Results for the Quarter Ended March 31, 2012

OPERATING HIGHLIGHTS

(NEW YORK — May 3, 2012) — ACI Worldwide, Inc. (NASDAQ:ACIW), a leading international provider of payment systems, today announced financial results for the period ended March 31, 2012. We will hold a conference call on May 3, 2012, at 8:30 a.m. EST to discuss this information. Interested persons may also access a real-time audio broadcast of the teleconference at www.aciworldwide.com/investors.

“ACI had a solid first quarter. Revenue from backlog grew 34% over prior-year as we concluded service implementations and added higher recurring maintenance and hosting revenues to our predictable business model,” said Chief Executive Officer Philip Heasley. “We also closed the S1 acquisition in mid-February and effected cost savings by the end of the first quarter which will amount to $33 million on an annualized basis. We remain excited about cross-selling opportunities that lie ahead of us now that the former S1 employees have joined the ACI family.”

FINANCIAL SUMMARY

Sales

Sales bookings in the quarter totaled $108.5 million. In the prior-year quarter sales bookings were $122.9 million. S1 contributed $24.4 million to sales in the quarter.

Backlog

60-month backlog increased $700 million to $2.317 billion as compared to $1.617 billion at December 31, 2011. 12-month backlog increased $158 million to $582 million as compared to $424 million at December 31, 2011. Contribution of the former S1 Corporation backlog accounted for $705 million of the rise in 60-month backlog and $174 million of the 12-month backlog during the quarter.

Revenue

Non-GAAP revenue increased $37.4 million, or 36%, over prior-year first quarter. Non-GAAP revenue excludes the impact of $4.3 million of deferred revenue that would have been recognized in the normal course of business by S1 but was not recognized due to GAAP purchase accounting requirements. GAAP revenue increased $33.1 million, or 32%, over prior-year first quarter. The acquisition of S1 Corporation contributed $22.5 million of revenue in the quarter for the period February 13-March 31, 2012.

Operating Expenses

Excluding $15.0 million of S1 acquisition related one-time expenses, operating expenses increased $27.2 million compared to the prior-year quarter primarily from the addition of S1. Total GAAP operating expenses for the quarter were $139.2 million.

Operating Income

Non-GAAP operating income increased $10.2 million, or 135%, compared to the prior-year quarter. GAAP operating income decreased $9.1 million compared to the prior-year quarter. Non-GAAP operating income excludes the deferred revenue adjustment due to purchase accounting as well as $15.0 million of S1 acquisition-related one-time expenses.

Adjusted EBITDA

Adjusted EBITDA increased to $31.1 million, growth of $14.4 million, or 86%, compared to the prior year quarter. Adjusted EBITDA excludes $15.0 million of acquisition related one-time expenses and the impact of $4.3 of million deferred revenue that would have been recognized in the normal course of business by S1 but was not recognized due to GAAP purchase accounting requirements.

Liquidity

We had $201.1 million in cash on hand as of March 31, 2012. The Company also paid $3.1 million in principal payments for the term credit facility during the first quarter 2012. Year to date to May 2, 2012, we repurchased 185,800 shares for $7.1 million. The maximum remaining dollar value of shares authorized for purchase under the stock repurchase program was approximately $68.0 million.

During Q1 2012, we received proceeds of $295 million from our credit facility to partially fund the purchase of S1 Corporation.

Operating Free Cash Flow

Operating free cash flow (“OFCF”) for the quarter was $4.0 million, a decrease of $8.3 million as compared to the March 2011 quarter.

Other Expense

Other expense for the quarter was $0.8 million, essentially flat as compared to other expense of $0.7 million in the March 2011 quarter.

Taxes

Income tax benefit in the quarter was $0.6 million, or a 23% effective tax rate, compared to income tax expense of $5.2 million, or a 76% rate, in the prior-year quarter. The income tax benefit for the quarter ended March 31, 2012 was favorably impacted by income in our foreign jurisdictions taxed as a lower rate and a loss in the US being taxed at a higher rate.

Net Income (loss) and Diluted Earnings Per Share

Net loss for the quarter ended March 31, 2012 was $1.8 million, compared to net income of $1.6 million during the same period last year, a reduction of $3.4 million.

Earnings (loss) per share for the quarter ended March 31, 2012 was $(0.05) per diluted share compared to $0.05 per diluted share during the same period last year. Excluding the impact of $15.0 million of S1 acquisition related one-time expenses and the impact of $4.3 of million deferred revenue that would have been recognized in the normal course of business by S1 but was not recognized due to GAAP purchase accounting requirements, earnings per share was $0.28 per diluted share.

Weighted Average Shares Outstanding

Total diluted weighted average shares outstanding were 36.7 million for the quarter ended March 31, 2012 as compared to 34.0 million shares outstanding for the quarter ended March 31, 2011. The number of weighted average shares outstanding was increased by 2.7 million due to the issuance of shares related to the acquisition of S1 Corporation. 7.1 million options to purchase shares, restricted share awards, common stock warrants and contingently issuable shares were excluded from the diluted earnings per share computation as their effect would have been anti-dilutive.

2012 Guidance

We are reiterating our annual guidance based upon what we are seeing in our business markets to date. Hence, guidance for calendar year is as follows: Revenue to achieve a range of $696-706 million, Operating Income of $99-104 million and Adjusted EBITDA of $165-170 million. Guidance for the year excludes the impact of professional fees and transaction-related expenses associated with the acquisition of S1 Corporation.

-End-

About ACI Worldwide

ACI Worldwide powers electronic payments for more than 800 financial institutions, retailers and processors around the world, with its broad and integrated suite of electronic payment software. More than 90 billion times each year, ACI’s solutions process consumer payments. On an average day, ACI software manages more than US$12 trillion in wholesale payments. And for more than 160 organizations worldwide, ACI software helps to protect their customers from financial crime. To learn more about ACI and understand why we are trusted globally, please visit www.aciworldwide.com. You can also find us on www.paymentsinsights.com or on Twitter @ACI_Worldwide.

For more information contact:

Tamar Gerber, Vice President, Investor Relations & Financial Communications

ACI Worldwide

+1 402 778 1990

invrel@aciworldwide.com

Non-GAAP Financial Measures

ACI Worldwide, Inc.

Reconciliation of Selected GAAP Measures to Non-GAAP Measures (1)

(unaudited and in thousands, except per share data)

To supplement our financial results presented on a GAAP basis, we use the non-GAAP measure indicated in the tables, which exclude certain business combination accounting entries and expenses related to the acquisition of S1, as well as other significant non-cash expenses such as depreciation, amortization and share-based compensation, that we believe are helpful in understanding our past financial performance and our future results. The presentation of these non-GAAP financial measures should be considered in addition to our GAAP results and are not intended to be considered in isolation or as a substitute for the financial information prepared and presented in accordance with GAAP. Management generally compensates for limitations in the use of non-GAAP financial measures by relying on comparable GAAP financial measures and providing investors with a reconciliation of non-GAAP financial measures only in addition to and in conjunction with results presented in accordance with GAAP. We believe that these non-GAAP financial measures reflect an additional way of viewing aspects of our operations that, when viewed with our GAAP results, provide a more complete understanding of factors and trends affecting our business.

Backlog is considered a non-GAAP financial measure as defined by SEC Regulation G. Our 60-month backlog estimate represents expected revenues from existing customers using the following key assumptions:

Estimates of future financial results are inherently unreliable. Our backlog estimates require substantial judgment and are based on a number of assumptions as described above. These assumptions may turn out to be inaccurate or wrong, including for reasons outside of management’s control. For example, our customers may attempt to renegotiate or terminate

their contracts for a number of reasons, including mergers, changes in their financial condition, or general changes in economic conditions in the customer’s industry or geographic location, or we may experience delays in the development or delivery of products or services specified in customer contracts which may cause the actual renewal rates and amounts to differ from historical experiences. Changes in foreign currency exchange rates may also impact the amount of revenue actually recognized in future periods. Accordingly, there can be no assurance that contracts included in backlog estimates will actually generate the specified revenues or that the actual revenues will be generated within the corresponding 60-month period.

Backlog should be considered in addition to, rather than as a substitute for, reported revenue and deferred revenue.

Forward-Looking Statements

This press release contains forward-looking statements based on current expectations that involve a number of risks and uncertainties. Generally, forward-looking statements do not relate strictly to historical or current facts and may include words or phrases such as “believes,” “will,” “expects,” “anticipates,” “intends,” and words and phrases of similar impact. The forward-looking statements are made pursuant to safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

Forward-looking statements in this press release include, but are not limited to, statements regarding: (i) our expectations related to annual cost savings expected from the S1 acquisition, and (ii) expectations and assumptions regarding 2012 financial guidance related to revenue, operating income and adjusted EBITDA.

All of the foregoing forward-looking statements are expressly qualified by the risk factors discussed in our filings with the Securities and Exchange Commission. Such factors include but are not limited to, risks related to the global financial crisis and the continuing decline in the global economy, restrictions and other financial covenants in our credit facility, volatility and disruption of the capital and credit markets and adverse changes in the global economy, risks related to the expected benefits to be achieved in the transaction with S1, , consolidations and failures in the financial services industry, the accuracy of management’s backlog estimates, the cyclical nature of our revenue and earnings and the accuracy of forecasts due to the concentration of revenue generating activity during the final weeks of each quarter, impairment of our goodwill or intangible assets, exposure to unknown tax liabilities, volatility in our stock price, risks from operating internationally, including fluctuations in currency exchange rates, increased competition, our offshore software development activities, customer reluctance to switch to a new vendor, the performance of our strategic product, BASE24-eps, the maturity of certain products, our strategy to migrate customers to our next generation products, ratable or deferred recognition of certain revenue associated with customer migrations and the maturity of certain of our products, demand for our products, failure to obtain renewals of customer contracts or to obtain such renewals on favorable terms, delay or cancellation of customer projects or inaccurate project completion estimates, business interruptions or failure of our information technology and communication systems, our alliance with International Business Machines Corporation (“IBM”), our outsourcing agreement with IBM, the complexity of our products and services and the risk that they may contain hidden defects or be subjected to security breaches or viruses, compliance of our products with applicable legislation, governmental regulations and industry standards, our compliance with privacy regulations, the protection of our intellectual property in intellectual property litigation, future acquisitions, strategic partnerships and investments and litigation, the risk that expected synergies, operational efficiencies and cost savings from the S1 acquisition may not be fully realized or realized within the expected time frame. For a detailed discussion of these risk factors, parties that are relying on the forward-looking statements should review our filings with the Securities and Exchange Commission, including our most recently filed Annual Report on Form 10-K, Registration Statement on Form S-4, and subsequent reports on Form 8-K.

ACI WORLDWIDE, INC. AND SUBSIDIARIES

CONSOLIDATED BALANCE SHEETS

(unaudited and in thousands, except share and per share amounts)

ACI WORLDWIDE, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS

(unaudited and in thousands, except per share amounts)

ACI WORLDWIDE, INC. AND SUBSIDIARIES

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS

(unaudited and in thousands)