Mariappa has signed a three-year contract to end his season-long stay at Reading having impressed during his 32 appearances at the club and provides manager Ian Holloway with some much-needed quality in defence.
"Playing there last season was a great challenge as it is is the biggest league in the world and you're playing against the best players, so when this opportunity came to me I jumped at it," Mariappa said.
"Selhurst Park is always a great place to play, the atmosphere has always been amazing and I've had some great games against this club.
"I want to prove I can play at this level and I'm sure that will be the same for everyone in the squad as we aim to stay in the Premier League."
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