The Danish centre-back, who spent last season with Fulham, has penned a five-year deal with the south London club.
"I'm extremely proud to be joining Crystal Palace and to be playing in the world's best football league," Andersen told the club website.
"The management of the club and Patrick Vieira have given me very strong assurance that they know my qualities, they believe in me and want me to play an important role in the team.
"I have a very positive impression of Patrick from the conversations I have had with him, and I have heard nothing but great things about the manager, the club and its plans for the future."
Welcome to Palace, Joachim Andersen! #CPFC | https://t.co/utMcYSDkhb
— Crystal Palace F.C. (@CPFC) July 28, 2021
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