Canadian firm SNC-Lavalin has agreed a £2.1bn takeover of Atkins.
The company has offered £20.80 per share with both boards having agreed to the deal.
Atkins chief executive Uwe Krueger will step down and be replaced by current chief financial officer Heath Drewett.
SNC-Lavalin has also set aside £5m in cash retention payments for senior Atkins managers to ensure they stay with the firm for at least 12 months.
The Atkins brand will remain during the takeover period but will be looked at in the long-term depending on client feedback.
The deal is expected to be completed by the third quarter of this year.
Neil Bruce, president and chief executive of SNC-Lavalin, said: “By combining two highly complementary businesses, we will increase our depth and breadth of services to position us as a premier partner to public and private sector clients.
“It also creates new revenue growth opportunities in key geographies by positioning us to capitalise on increased cross-selling and the opportunity to win and deliver major projects in new regions.
“I look forward to welcoming Atkins’ employees into our combined company. Together, we will become part of a larger global organisation that will open the door to new opportunities for further growth and development.”
