Engineer WSP has acquired its fellow Canadian rival MMM for US$330m.
MMM has about 2,000 employees and is one of the largest privately owned engineering consultancies in Canada.
WSP now has 8,500 employees in the country, with a global workforce of 34,000.
The "arrangement agreement" was announced in August.
David Ackert, president of WSP in Canada, said: "I’m delighted about this acquisition and that our two firms are joining forces.
"The coming together of these two like-minded firms will enable us to pursue our growth strategy and strengthen our foundation across Canada by increasing our ability to deliver superior value to our clients, shareholders and employees."
Hugo Blasutta, MMM’s chief executive, said: "As we join WSP, a firm with similar values to MMM and a complementary business model, we will have an opportunity to continue our journey of growth.
"We also look forward to providing additional value for our employees and clients through our enhanced expertise and expanded network."