The 28-year-old centre-back, who spent the second half of last season on loan at West Ham, is set to complete his medical on Friday. This move comes as Palace are searching for a replacement for Maxence Lacroix after selling the France defender to Chelsea.
Palace have also informed Manchester City that Adam Wharton is not for sale, despite the England midfielder being a target for the Premier League champions. Wharton has three years left on his current deal at Palace and it is thought the club would demand a sizeable fee to consider selling him. Liverpool and Chelsea have both shown interest in Wharton in the past, with the latter monitoring his situation in case City make a bid for Enzo Fernández.
Palace are also hoping to bring in a midfielder before the deadline, with Kévin Danois from Auxerre and Lamine Camara from Monaco being their top targets. The club are determined to keep Wharton, who has been a key player for them, and are not willing to sell him to City.