Exhibit 99.1

Pegasystems Announces Financial Results for Third Quarter and Nine Months of 2015

Achieved Strong License and Cloud Revenue Growth While Increasing Backlog by 14% over Q3 2014

CAMBRIDGE, Mass. – October 27, 2015 – Pegasystems Inc. (NASDAQ: PEGA), the software company empowering the world’s leading enterprises with strategic business applications, today announced results for its third quarter and nine months ended September 30, 2015.

“We are very pleased with our strong performance this quarter and through the first nine months of 2015,” said Alan Trefler, Founder and CEO of Pegasystems. “Once again, we exceeded our revenue goals while building backlog during what is often our most challenging quarter. Our strategy to reach a broader target base is bearing fruit, and we are seeing an increase in the number and size of deals from new logos, while continuing to expand our business with existing clients.”

SELECTED GAAP & NON-GAAP RESULTS (1)

Cash: Total cash, cash equivalents, and marketable securities at September 30, 2015 was $224 million, up 6% from 2014 year-end.

Cash generated from operations for the nine months of 2015 was $55 million. Free Cash Flow, which we define as operating cash flow less Cap Ex, was $45 million for the nine months of 2015.

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License and Cloud Backlog: The Company computes license and cloud backlog by adding billed deferred license and cloud revenue and off-balance sheet license and cloud commitments, which is business that is contracted, unbilled, and not recorded on the Company’s balance sheet.

License and Cloud Backlog (1)

“Our results to date demonstrate continued strong execution toward our financial goals and evidence of transaction in the market across our product offerings,” said Rafe Brown, Pegasystems CFO. “While the mix of deal types in a given quarter will significantly influence our results for that period, our growth in License and Cloud revenue, along with continued strength of our total backlog, indicates that our investments in sales, marketing, and product are paying off. We are thus continuing our investments in these areas and even accelerating some of our 2016 investments as a reflection of our confidence in the long-term prospects for the company.”

Quarterly Conference Call

Pegasystems will host a conference call and audio-only Webcast associated with this announcement at 5:00 p.m. EDT today. A live audio webcast of the conference call, together with detailed financial information, can be accessed through the Company’s Website at www.pega.com/about/investors. Dial-in information is as follows: 1-877-407-3982 (domestic) or 1-201-493-6780 (international). To listen to the Webcast, log onto www.pega.com at least five minutes prior to the event’s broadcast and click on the Webcast icon in the Investors section. A replay of the call will also be available on www.pega.com by clicking the Earnings Calls link in the Investors section.

Discussion of Non-GAAP Financial Measures

To supplement financial results presented in accordance with Generally Accepted Accounting Principles in the U.S. (“GAAP”), the Company provides non-GAAP measures, including in this release. Pegasystems’ management utilizes a number of different financial measures, both GAAP and non-GAAP, in analyzing and assessing the overall performance of the business, for making operating decisions, and for forecasting and planning for future periods. The Company’s annual financial plan is prepared both on a GAAP and non-GAAP basis, and both are approved by our board of directors. In addition and as a consequence of the importance of these measures in managing the business, the Company uses non-GAAP measures and financial performance results in the evaluation process to establish management’s compensation.

The non-GAAP measures exclude the effects of certain business combination accounting entries, stock-based compensation expense, amortization of acquired intangibles, acquisition-related and restructuring expenses, and the benefit associated with favorable settlements of certain indemnification claims and indirect tax liabilities. The Company believes that these non-GAAP measures are helpful in understanding its past financial performance and its anticipated future results. These non-GAAP financial measures are not meant to be considered in isolation or as a substitute for comparable GAAP measures and should be read only in conjunction with the Company’s consolidated financial statements prepared in accordance with GAAP. A reconciliation of the Company’s GAAP to non-GAAP measures is included in the financial schedules at the end of this release.

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Forward-Looking Statements

“Safe harbor” statement under the Private Securities Litigation Reform Act of 1995: Certain statements contained in this press release may be construed as “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995. The words “expect,” “anticipate,” “intend,” “plan,” “believe,” “could,” “estimate,” “may,” “target,” “strategy,” “is intended to,” “project,” “guidance” and similar expressions, among others, identify forward-looking statements, which speak only as of the date the statement was made. These statements are based on current expectations and assumptions and involve various risks and uncertainties, which could cause the Company’s actual results to differ from those expressed in such forward-looking statements. These risks and uncertainties include, among others, variation in demand for our products and services and the difficulty in predicting the completion of product acceptance and other factors affecting the timing of our license revenue recognition; the ongoing consolidation in the financial services, insurance, healthcare, and communications markets; reliance on third party relationships; the potential loss of vendor specific objective evidence for our time and materials professional services arrangements; the inherent risks associated with international operations and the continued weakness in international economies; foreign currency exchange rates; the financial impact of the Company’s past acquisitions and any future acquisitions; and management of the Company’s growth. Further information regarding these and other factors which could cause the Company’s actual results to differ materially from any forward-looking statements contained in this press release is contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 and other recent filings with the Securities and Exchange Commission. These documents are available on the Company’s website at http://www.pega.com/about/investors. The forward-looking statements contained in this press release represent the Company’s views as of October 27, 2015. Investors are cautioned not to place undue reliance on such forward-looking statements and there are no assurances that the matters contained in such statements will be achieved. Although subsequent events may cause the Company’s view to change, except as required by applicable law, the Company does not undertake and specifically disclaims any obligation to publicly update or revise these forward-looking statements whether as the result of new information, future events or otherwise. The statements should therefore not be relied upon as representing the Company’s view as of any date subsequent to October 27, 2015.

About Pegasystems

Pegasystems (NASDAQ: PEGA) develops strategic applications for marketing, sales, service, and operations. Pega’s applications streamline critical business operations, connect enterprises to their customers seamlessly in real-time across channels, and adapt to meet rapidly changing requirements. Pega’s Global 2000 customers include many of the world’s most sophisticated and successful enterprises. Pega’s applications, available in the cloud or on-premises, are built on its unified Pega 7 platform, which uses visual tools to easily extend and change applications to meet clients’ strategic business needs. Pega’s clients report that Pega gives them the fastest time to value, extremely rapid deployment, efficient re-use and global scale. For more information, please visit us at www.pega.com.

Press Contacts:

Lisa Pintchman

Pegasystems Inc.

lisa.pintchman@pega.com

(617) 866-6022

Twitter: @pega

Investor Contact:

Sheila Ennis

ICR for Pegasystems

PegaInvestorRelations@pega.com

617-866-6077

All trademarks are the property of their respective owners.

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Pegasystems Inc.

Unaudited Condensed Consolidated Statements of Operations

($ in thousands, except per share amounts)

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PEGASYSTEMS INC.

RECONCILIATION OF SELECTED GAAP MEASURES TO NON-GAAP MEASURES (1)

($ in thousands, except per share amounts)

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PEGASYSTEMS INC.

RECONCILIATION OF SELECTED GAAP MEASURES TO NON-GAAP MEASURES (1)

($ in thousands, except per share amounts)

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PEGASYSTEMS INC.

FOOTNOTES FOR RECONCILIATION OF

SELECTED GAAP MEASURES TO NON-GAAP MEASURES

Revenue: Business combination accounting rules require that we determine the fair value of the deferred revenue liability for contractual obligations assumed primarily from our acquisition of Antenna Software, Inc. and its subsidiaries (“Antenna”) in October 2013. In post-acquisition reporting periods, we recognize revenue for the fair value of these contracts, when all the revenue recognition criteria are satisfied, instead of the revenue that would have been recognized by Antenna as an independent company. We add back the effect of the deferred revenue fair value adjustment in non-GAAP revenue to reflect the full amount of these revenues to provide a more complete comparison of the revenue guidance to peer companies. No adjustments were made to revenue for the nine months of 2015.

Amortization of intangible assets: We have excluded the amortization expense of intangible assets from our non-GAAP operating expenses and net earnings measures. Amortization of intangible assets is inconsistent in amount and frequency and is significantly affected by the timing and size of our acquisitions. Investors should note that the use of intangible assets contributed to our revenues earned during the periods presented and will contribute to our future period revenues as well. Amortization of intangible assets will recur in future periods.

Stock-based compensation expense: We have excluded stock-based compensation expense from our non-GAAP operating expenses and net earnings measures. Although stock-based compensation is a key incentive offered to our employees, and we believe such compensation contributed to the revenues earned during the periods presented and will contribute to the generation of future period revenues, we continue to evaluate our business performance excluding stock-based compensation expense.

Acquisition-related and restructuring expenses: We have excluded the effect of acquisition-related and restructuring expenses from our non-GAAP operating expenses and net earnings measures. We incurred direct and incremental expenses associated with the Antenna and 2014 acquisitions. These acquisition-related expenses were primarily professional fees to affect the acquisitions. We have also incurred restructuring expenses related to the integration of the Antenna acquisition, which we generally would not have otherwise incurred in the periods presented as a part of our continuing operations. Restructuring expenses consist primarily of lease exit costs. We believe it is useful for investors to understand the effects of these items on our total operating expenses.

Indemnification claim and indirect tax settlements: We reached an agreement with the former shareholders of Antenna to release a portion of the funds held in escrow as security for their indemnification obligations to us in settlement of the outstanding indemnification claims. The settlement resulted in a benefit to cost of revenue and operating expenses in the first quarter of 2015. In addition, we favorably settled indirect tax liabilities related to the Antenna acquisition, which resulted in a benefit to operating expenses in the first quarter of 2015. We believe the benefit associated with the settlements of the Antenna indemnification claims and indirect tax liabilities is not representative of our ongoing business, and we have excluded the effects of these items from our non-GAAP operating results and net earnings measures.

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The GAAP income tax effects were calculated using an effective tax rate of 36.0% and 31.8% for the nine months of 2015 and 2014, respectively. The non-GAAP income tax effects were calculated using an effective non-GAAP tax rate of 34.3% and 32.6% for the nine months of 2015 and 2014, respectively.

The differences between our GAAP and non-GAAP effective tax rates in the third quarter and nine months of 2015 primarily relate to the favorable impact of stock-based compensation expense adjustments on non-GAAP effective tax rates.

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Pegasystems Inc.

Unaudited Condensed Consolidated Balance Sheets

(in thousands)

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Pegasystems Inc.

Unaudited Condensed Consolidated Statements of Cash Flows

(in thousands)

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Pegasystems Inc.

Historical License and Cloud Backlog

(in thousands)

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