The winger joined Man United from the Eagles in 2013 but failed to establish himself as a regular starter at Old Trafford.
He was eventually sent back to his boyhood club on loan this season and has now made the move permanent.
Speaking to Palace’s official website about why he left United, Zaha said: “I wasn’t getting much game time at Man United so I took the opportunity to come back on loan this season. I now have the chance to make the move permanent and to come home to Selhurst Park is something I’m delighted about.
“For me to be a better player, I need to play more games, and having a gaffer that I know has great trust in me gives me the confidence I need to help me improve my game.
“I started playing here when I was eight years of age and my family live local and to have the opportunity to take the field in the Premier League for this club is a dream come true.”
The 22-year-old was Sir Alex Ferguson’s last ever signing when he joined Man United for £15m but he struggled in the red shirt. Despite showing occasional flashes of the talent he quite clearly has, he progressed poorly and rarely featured in the first team.
Various murmurs have indicated that a poor attitude contributed to his failed spell at the club, which is frustrating for United fans given his potential.
It is not the first time a player at United has failed to unlock his talent, with Anderson also seemingly on his way out of the club. It is unlikely that Zaha will be the last.