Jean is representing the international organization of Francophone states who have inked a deal with the Games since 2004 on the use of French, which is one of the two official languages of the Olympic movement.
Negotiations for the London deal had been lengthy, due to what Jean had earlier called a reluctance on their part to accept that French had a major role to play at the Games.
But the deal signed Thursday was heralded by both sides.
It sets out the areas where French must be used, including on billboards, in communication with athletes and in services.
Among its components are the deployment of French-speaking Facebook moderators who will help London organizers make sure their social media communications are in both languages.
Jean signed the agreement with London Games CEO Sebastien Coe, who addressed the mostly Francophone crowd in Quebec City entirely in English.
"Wherever possible we've sought to find innovative approaches to the use of French with the aim of delivering our information to its audience in the most efficient way," he said.
For example, French versions of spectator guides will be downloadable via mobile phones.
Jean will attend the Games in August to monitor how well the deal is carried out. She called the agreement a team effort.
"Previous Games have left a linguistic legacy that's inspired London," she said.
The 2010 Olympics in Vancouver were heralded by La Francophonie for setting a gold standard for the use of French, despite criticisms levied at its CEO.
John Furlong was pilloried for not learning enough French during his tenure as Olympic boss and for the fact that many considered the opening ceremonies to not include enough French language elements.