Sorrell's existing contract was due to run until the end of next season but the 30-year-old has been tied down to a longer deal.
Director of rugby Alan Gaffney said: "Kevin is a valuable member of our squad and we're delighted to have secured the long-term future of someone who has been one of our most consistent performers this season.
"Kevin has played at Saracens all his life and he continues to be a terrific servant for the club. He has taken on extra responsibilities this season with the vice-captaincy and he has an important role to play in the club's future so we're very pleased he has agreed to extend his contract."
Sorrell, twice voted Sarries' player of the season, said: "I'm really delighted. Alan Gaffney came to me a few weeks ago and asked if I'd consider extending my contract and we got things sorted out pretty quickly after that.
"I'm really enjoying my rugby this year and there is a good atmosphere at the club. It's an enjoyable place to be and that is reflected in what we are doing on the pitch. We're playing some good rugby and there's a solid structure in place that also allows us to have a free reign to attack what we see.
"This is an exciting time to be at Saracens so extending my contract for another two years was an easy decision to make."