The company, which has previously used the brand strapline “It’s not easy being green” was found guilty of hacking into Greenpeace’s computers and stealing information.
The energy firm’s former head of nuclear production security was sentenced to three years in jail by a French court, as was his deputy.
EDF must also pay Greenpeace €500,000 (£428,910) in damages. Its French and UK offices declined to comment.
Greenpeace UK’s executive director, John Sauven, says: “As one of the six companies with a monopoly over electricity supply in this country and a major sponsor of the Olympics, EDF has a duty to come clean.”
The news comes as EDF put up its energy prices in the UK. Its customers will now pay 15.4% more for gas and 4.5% more for electricity.
The firm reported a 3.2% rise in group sales to €47.2bn (£40.5bn) for the nine months to September.