The Swiss team confirmed the news yesterday, after agreeing to new contracts with the pair, on the eve of this weekend's Hungarian Grand Prix.
Peter Sauber, the team principal, said: "Kamui has grown into his role extremely well this year. Though it is only his second full Formula One season, he is already taking on the responsibilities that naturally fall to the more experienced driver.
"We had an option of working with him in 2012 and there was never any doubt that we would take it."
Perez already had a contract for 2012 after agreeing a multi-year deal before he signed. Sauber said that the Mexican's pace - and recovery from his big accident at the Monaco Grand Prix - had shown he was right to have faith in him.
"After the accident in Monaco he [Sergio] demonstrated that he can handle difficult situations too.," Sauber said. "With a rookie that always entails a certain risk, of course, but clearly it has paid off."
Perez said: "It is very good to have continuity and this way I can intensively prepare with my race engineer for what will be my second season. The summer break will be very good for me because since my accident in Monaco it has been a busy time."