Speroni, who has been the fans' Player of the Year for the last three seasons, joined Palace from Dundee for £500,000 in July 2004.
He has gone on to make almost 200 appearances for the Eagles and is widely regarded as one of the best shot-stoppers in the division.
"Everyone connected with the club knows Julian is a special keeper and a thoroughly decent person," Palace co-chairman Steve Parish told the club's official website. "I'm absolutely delighted he has agreed to commit his future to Crystal Palace football club.
"With Julian, Darren Ambrose and Paddy McCarthy all signing long-term deals it shows the fans the commitment we have to making this club a success and getting back to the top of the division where we belong."