The financial terms of the arrangement were not disclosed, but the property will be rebranded as FanDuel Sportsbook and Horse Racing.
The operator would also undertake a major revamp of the venue and open a retail sportsbook at the location.
The agreement will see FanDuel’s sports betting license in Illinois transferred from the Boyd Gaming-owned Par-A-Dice Casino to the racing venue.
The operator went live with its online and mobile sportsbook in the state in September through its partnership Boyd.
“We are delighted to partner with Fairmount Park to continue bringing high quality horse racing and soon additional entertainment experiences via our sportsbook to the region,” FanDuel chief executive Matt King said.