Seri, who has been linked with Chelsea and Arsenal in recent weeks and was a reported target for Barcelona last summer, has signed a four-year contract that promises to keep him at Craven Cottage until June 2022.
The deal, which for now remains subject to Seri formally being granted a work permit, also includes the option of extending the contract by a further year to 2023.
"It was a long day yesterday so it was great to get the move finalised," Seri told FulhamFC.com.
"Now, I'm ready to get started and looking forward to meeting the squad and getting to know them, the head coach and his staff better," the Ivory Coast international added.
I’m delighted to announce that @FulhamFC has signed midfielder Jean-Michael Seri from Nice. He’s been at the very top of our target list for a long time. This is a big day for Fulham. We’re ecstatic that Jean-Michael is joining our squad as we return home to the @premierleague! pic.twitter.com/YdHRd6olzl— Tony Khan (@TonyKhan) July 12, 2018
Fulham director Tony Khan said "Jean Michaël arrives with Premier League qualities as well as great promise for the future, which is why he has been at the very top of our target list for a long time.
"So, this is a big day for everyone associated with Fulham and working at Motspur Park, and I trust all Fulham supporters are collectively as thrilled and ecstatic as we are that Jean Michaël will be joining our squad as we return home to the Premier League!"