Exhibit 99.1

Willbros Reports First Quarter 2017 Results

HOUSTON, TX, May 2, 2017 — Willbros Group, Inc. (NYSE: WG) today announced financial results for the first quarter of 2017. The Company reported a net loss of $17.8 million, or $(0.29) per diluted share, in the first quarter of 2017 on revenue of $163.9 million, compared to 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.

An operating loss of $14.9 million in the first quarter of 2017 compares to an operating loss of $9.5 million in the first quarter of 2016. Included in the first quarter of 2017 operating loss are $0.8 million of other charges, primarily related to severance and professional fees, which compares to $3.7 million of other charges in the first quarter of 2016, which were primarily related to equipment and facility lease abandonment charges.

Michael Fournier, President and CEO, commented, “As expected, our first quarter of 2017 revenue was similar to the fourth quarter of 2016 as the work associated with awards announced in early March had minimal impact in the first quarter. We fell short in our operating income expectations due to a project loss in our Oil & Gas segment coupled with lower than anticipated net contract margin in our Utility T&D segment. With the backlog growth in the first quarter, coupled with $42 million in new awards in April, we see a significant increase in revenue for the second quarter of 2017 and anticipate an improvement in operating performance. Finally, we have signed a non-binding letter of intent to sell our U.S. tank services business.”

Backlog

The Company’s twelve-month and total backlog increased for the second consecutive quarter. Twelve-month backlog of $528.4 million at March 31, 2017 increased $108.5 million, or approximately 26% from December 31, 2016 as all segments showed positive gains. Total backlog of $852.5 million at March 31, 2017, increased $60 million, or approximately 8% from December 31, 2016.

CONTACT:

Stephen W. Breitigam

VP Investor Relations

Willbros

713-403-8172

Segment Operating Results

Utility T&D

The Utility T&D segment reported revenue of approximately $115.5 million for the first quarter of 2017, a 10% increase compared to the fourth quarter of 2016. The segment reported operating income of $0.8 million in the first quarter of 2017 compared to operating income of $2.1 million in the fourth quarter of 2016. The lower operating income was primarily generated in the segment’s electric transmission business due to a change in the mix of work between periods which led to higher indirect costs and margin erosion.

Oil & Gas

For the first quarter of 2017, the Oil & Gas segment reported revenue of $22.4 million and an operating loss of $7.3 million, a $1.6 million increase in operating loss from the fourth quarter of 2016 when this segment generated $23.3 million in revenue. The increased operating loss was primarily due to a $1.0 million project loss in our integrity construction business coupled with lower activity in our mainline pipeline and facilities construction businesses.

Canada

Canada reported revenue of $26.0 million for the first quarter of 2017, a $9.8 million reduction when compared to the fourth quarter of 2016. The segment reported an operating loss of $3.3 million in the first quarter of 2017 compared to an operating loss of $1.8 million in the fourth quarter of 2016. The increased operating loss was impacted by lower revenue volume across the segment and lower margins in our construction and maintenance business as work transitioned to new contracts.

Liquidity

Total liquidity (defined as cash and cash equivalents plus revolver availability) was $49.5 million at March 31, 2017, which includes $36.7 million of cash and cash equivalents. Liquidity levels decreased $17.2 million from $66.7 million at December 31, 2016 primarily attributed to reduced revolver availability due to additional letters of credit issued in the quarter that supports new work. There were no revolver borrowings at March 31, 2017.

Guidance

Van Welch, Willbros Chief Financial Officer, commented, “With the increase in backlog and the new awards, we believe revenue will increase significantly and operating income will improve for the second quarter of 2017. We are re-confirming our revenue guidance for the year of $775 to $825 million excluding our tank services business.”

Conference Call

In conjunction with this release, Willbros has scheduled a conference call, which will be broadcast live over the Internet, on Wednesday, May 3, 2017 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, 2017 and may be accessed by calling 877-344-7529 (U.S. Toll Free), 855-669-9658 (Canada Toll Free) or 412-317-0088 (International) using pass code 10106451. 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 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

###

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.