The 29-year-old made the switch to Selhurst Park in 2011 from Turkish outfit Genclerbirligi, and will now remain with Tony Pulis' men until 2017.
Jedinak is a popular figure among Palace fans after skippering the side back to the Premier League for the first time since 2005 last season.
And the central midfielder is thrilled to extend his stay.
Speaking to the club's official website, he said: "I'm ecstatic to put pen to paper on a new contract.
"I've been a part of this football club for two and a half years and I've enjoyed every moment of that.
"The first season was great and the second obviously ended in us getting promoted and now we're in the Premier League where we want to be, so I'm really happy here and pleased that I've done this.
"I've built some strong relationships with players here and I've tried to make myself available to every player that comes through the gates and make them feel welcome and part of what we do.
"Everyone knows what we're about here and I have no doubts that we'll continue to push forward."
Palace have endured a difficult start to the Premier League season, and prop up the table with just seven points taken from 13 fixtures.
Pulis will look for his win as Palace boss in Tuesday's home fixture with West Ham.
