Palace had a bid for Wickham accepted by Sunderland last week and the 22-year-old has now joined the club on a five-year deal despite signing a new contract with the Black Cats at the turn of the year.
The England U21 striker scored five goals in three games towards the end of the 2013/14 season to help preserve Sunderland’s Premier League status, but he managed just six in the whole of last season.
Wickham joined Sunderland in an £8m transfer from Ipswich four years ago and scored a total of 15 goals in 91 appearances during his time on Wearside.
“I needed a fresh start. I had four years up north and it’s been a bit stop-start,” the striker told Palace’s official website.
“Now I’ve come back home and I can settle down and see my family a bit more and hopefully let my football do the talking.”
Wickham becomes Palace’s fourth summer recruit after the south London club completed the loan signing of Patrick Bamford from Chelsea and permanent deals for France midfielder Yohan Cabaye and goalkeeper Alex McCarthy.
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