The hotel made the announcement Monday. Flamingo President Don Marrandino cited the success of Donny and Marie's 90-minute greatest-hits multimedia show, which opened September 9.
They will continue to appear at the Flamingo Showroom through October 2010. Financial terms weren't disclosed.
Donny and Marie took over as Flamingo headliners after Toni Braxton's show ended in April due to Braxton's health concerns.