Speroni had been a target of Fulham and it was thought Palace might sell him in January if he did not sign a contract.
Co-chairman Steve Parish told the club website: "Everyone connected with the club knows Julian is a special keeper."
He continued: "I'm absolutely delighted he has agreed to commit his future to Crystal Palace.
"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."
Source: BBC Sport
Source: BBC Sport