The 30-year-old had been expected to join the F1 outfit following months of rumours after he visited the team's headquarters after the Singapore Grand Prix in September.
"I am very happy that we found common ground," Sky Sports News quotes Sutil as saying. "Although I have known for a while where I wanted to go, in the end the negotiations took a bit longer than planned. However, now I will have all the more reason to celebrate during the Christmas season.
"After six good years driving for Force India, with a lot of highlights, it's now time to embark on a new challenge. I am determined to do my part in order to have a successful future together with the Sauber F1 team. The long and successful tradition in motorsport, combined with an impressive factory and one of the best wind tunnels in F1, have been fascinating me for a long time."
The second seat is yet to be confirmed, but it has been reported that Esteban Gutierrez will stay with the team for a second season.