The Nuclear Atkins Assystem Alliance, to be based in France, will help both companies to address demand in countries developing nuclear power capacity and will provide services to new build projects and across the entire nuclear fuel cycle.
Each partner will continue to serve its home markets of the UK and France as separate entities.
The International Atomic Energy Agency (IAEA) has said that more than 30 countries are already using nuclear power and another 30 are considering development. These countries represent a total market of more than 200 new reactors over the next 20 years.
Together, Atkins and Assystem have 27,000 employees, of which 3,000 are professionals with nuclear skills. They are already working together on the ITER international nuclear fusion research project in the south of France, having been selected last April as part of the Engage consortium to act as Building Architect Engineer.
Atkins chief executive Keith Clarke said: "Nuclear engineering is a key part of Atkins' strategy going forward. The alliance with Assystem will give us a strong platform from which to deliver nuclear services to emerging international markets. The combination of our collective nuclear expertise will position us superbly to pursue opportunities in a broader array of markets with a wider range of services which go beyond our considerable presence in our own home markets."