Chelsea striker Sinclair signed on loan on Thursday for the rest of the season as Eagles boss Neil Warnock looks to strengthen his attacking options.
He had been on loan at Charlton but had hardly figured for the Addicks, so Chelsea recalled him ahead of today's loan deadline.
"It feels great to sign for a club like Palace," said Sinclair. "Hopefully I can help spark the club to promotion.
"It's been a difficult month or so at Charlton but I hope to have more playing time here. I want to score goals and hopefully the club can go up.
"Obviously I'm not playing at Chelsea -- so this is a great chance for me to get some experience. I just want to play football."