The 20-year-old Frenchman has made three substitute appearances for Pompey since signing for former manager Alain Perrin from Barcelona's youth ranks in 2005, and has had spells on loan at Bournemouth and Preston.
"I want to show people what I can do here and help the players," he told Palace's official website.
"It's going to be tough to get into the team but I hope to get some games. There is a lot of quality here. If everything goes well, I could be here a bit longer."