Cech, 30, is now tied to Stamford Bridge until June 2016.
"I am really happy to be part of this great club for another four years," he said in a statement released by his PR company.
"I hope the next four years will be as successful as the last eight years I have been at the club."
Cech has made 369 appearances for the club since joining from Rennes in 2004, more than any other foreign player in the Blues’ history.
Just under half of these games have seen Cech keep clean sheets, winning Premier League awards in 2005 and 2010.
In addition to this year’s Champions League, the Czech Republic international has won three Premier League titles, four FA Cups and two Carling Cups.