Exhibit 99.1

Willbros Reports First Quarter 2016 Results

HOUSTON, TX, May 2, 2016 — Willbros Group, Inc. (NYSE: WG) today announced financial and operating results for the first quarter of 2016. The Company reported a net loss of $15.2 million, or $(0.25) per diluted share, in the first quarter of 2016 on revenue of $199.0 million, compared to a net loss of $9.8 million, or $(0.20) per diluted share, in the first quarter of 2015 on revenue of $250.4 million. Net loss before special items was $9.2 million, or $(0.16) per diluted share, in the first quarter of 2016, compared to a net loss before special items in the first quarter of 2015 of $28.6 million, or $(0.57) per diluted share, and a $17.3 million net loss before special items, or $(0.28) per diluted share, in the fourth quarter of 2015.

An operating loss of $9.5 million in the first quarter of 2016 compares to a $21.3 million operating loss in the first quarter of 2015, an $11.8 million improvement. The Company’s first quarter of 2016 operating results include a $0.7 million loss related to a business that we have exited and $3.7 million of other charges primarily related to equipment and facility lease abandonment charges. Excluding these special items, the operating loss before special items was $5.1 million in the first quarter of 2016, which was a $1.8 million improvement from the Company’s operating loss before special items of $6.9 million in the fourth quarter of 2015. Adjusted EBITDA from continuing operations before special items for the first quarter of 2016 was $0.8 million, a $3.9 million improvement from Adjusted EBITDA from continuing operations before special items in the fourth quarter of 2015.

Michael J. Fournier, President and CEO, commented, “As we expected, our first quarter operating loss before special items showed a slight sequential improvement from the fourth quarter of 2015. Operating income before special items generated by our Utility T&D segment was partially offset by operating losses before special items in our Oil & Gas and Canada segments. The energy sector remains challenging as our customers balance their capital and maintenance spend versus liquidity concerns. Conversely, the utility transmission and distribution market remains strong. We continue to assess our revenue opportunities to appropriately adjust our cost structure. In addition, we remain focused on building backlog with our twelve month backlog up 6% whereas our total backlog at March 31, 2016 was down 5% from our year-end 2015 level.”

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Included in this press release are certain non-GAAP financial measures, including revenue, operating income (loss), net income (loss) and Adjusted EBITDA from continuing operations before special items. A related reconciliation of each of these non-GAAP measures is included in the accompanying schedules.

Backlog

At March 31, 2016, Willbros reported total backlog of $783.3 million compared to $826.8 million at December 31, 2015. Twelve month backlog of $457.3 million at March 31, 2016 increased $25.1 million, or approximately 6%, from December 31, 2015 as both Oil & Gas and Utility T&D showed positive gains.

Segment Operating Results

Utility T&D before special items

Utility T&D reported revenue of approximately $97.3 million for the first quarter of 2016, virtually flat compared to the fourth quarter of 2015. For the first quarter of 2016, the Utility T&D segment reported operating income of $2.5 million compared to an operating loss of $1.5 million in the fourth quarter of 2015.

Oil & Gas before special items

For the first quarter of 2016, the Oil & Gas segment generated revenue of $58.7 million and an operating loss of $6.5 million, a $0.9 million increase in operating loss from the fourth quarter of 2015 when this segment generated $76.6 million in revenue. The revenue decline was primarily due to lower activity in our pipeline and northeast business units, with the corresponding margin loss contributing to the operating loss.

Canada before special items

Canada reported revenue of $42.5 million for the first quarter of 2016, virtually identical to the fourth quarter of 2015. For the first quarter of 2016, the Canada segment generated an operating loss of $1.0 million compared to operating income of $0.2 million in the fourth quarter of 2015. Operating loss in the first quarter of 2016 was impacted by lower gross contract margins in the fabrication business and a reduction in gains on equipment sales.

Liquidity and Debt

Total liquidity (defined as cash and cash equivalents plus revolver availability) was $83.8 million at March 31, 2016 including $51.7 million of cash and cash equivalents. There were no revolver borrowings at March 31, 2016 and currently there are none.

During the first quarter of 2016, the Company used proceeds from a small asset sale to make a $3.1 million term loan payment. At March 31, 2016, the principal amount due on this debt facility was $92.2 million.

Guidance

Van Welch, Willbros Chief Financial Officer, commented, “Both our Oil & Gas and Canadian businesses continue to face difficult challenges in this current market and visibility into the latter half of the year is not clear. Therefore, for 2016, we now expect annual revenue to range between $825 million to $900 million. Near term, we expect the second quarter of 2016 revenues and operating income before special items to improve over the first quarter of 2016. In conjunction with our lower revenue expectation, we have taken additional steps to reduce our indirect, equipment and SG&A costs by $9 - $10 million for the remainder of the year. We anticipate recording employee severance costs and equipment impairment charges totaling $2.0 million during the second quarter of 2016.”

Conference Call

In conjunction with this release, Willbros has scheduled a conference call, which will be broadcast live over the Internet, on Tuesday, May 3, 2016 at 10:00 a.m. Eastern Time (9:00 a.m. Central Time).

For those who cannot listen to the live call, a replay will be available through May 10, 2016 and may be accessed by calling 877-660-6853 or 201-612-7415 using pass code 13636365#. Also, an archive of the webcast will be available shortly after the call on www.willbros.com.

Willbros is a specialty energy infrastructure contractor serving the oil and gas and power industries with offerings that primarily include construction, maintenance and facilities development services. For more information on Willbros, please visit our web site at www.willbros.com.

This announcement contains forward-looking statements. All statements, other than statements of historical facts, which address activities, events or developments the Company expects or anticipates will or may occur in the future, are forward-looking statements. A number of risks and uncertainties could

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cause actual results to differ materially from these statements, including unanticipated accounting or other issues regarding any material weaknesses in internal control over financial reporting; inability of the Company or its independent auditor to confirm relevant information or data; unanticipated issues that prevent or delay the Company’s independent auditor from completing its review of financial statements or that require additional efforts, procedures or review; the untimely filing of financial statements; pending and potential investigations and lawsuits; the identification of one or more issues that require restatement of one or more other prior period financial statements; ability to remain in compliance with, or obtain additional waivers or amendments under, the Company’s existing loan agreements; the existence of other material weaknesses in internal control over financial reporting; contract and billing disputes; availability of quality management; availability and terms of capital; changes in, or the failure to comply with, government regulations; the promulgation, application, and interpretation of environmental laws and regulations; future E&P capital expenditures; oil, gas, gas liquids, and power prices and demand; the amount and location of planned pipelines; development trends of the oil, gas, and power industries; as well as other risk factors described from time to time in the Company’s documents and reports filed with the SEC. The Company assumes no obligation to update publicly such forward-looking statements, whether as a result of new information, future events or otherwise, except as may be required by law.

SCHEDULES TO FOLLOW

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WILLBROS GROUP, INC.

(In thousands, except per share amounts)

Adjusted EBITDA from continuing operations is not a financial measurement recognized under U.S. generally accepted accounting principles, or U.S. GAAP. When analyzing our operating performance, investors should use Adjusted EBITDA from continuing operations in addition to, and not as an alternative for, net income, operating income, or any other performance measure derived in accordance with U.S. GAAP, or as an alternative to cash flow from operating activities as a measure of our liquidity. Because all companies do not use identical calculations, our presentation of Adjusted EBITDA from continuing operations may be different from similarly titled measures of other companies.

Supplemental Schedule of Special Items