Ferrari protege Raffaele Marciello will be Sauber's test and reserve driver for the 2015 Formula 1 season.
Marciello, a long-time member of Ferrari's driver academy programme, made his F1 testing debut for the Maranello squad in Abu Dhabi last month.
The 20-year-old Italian will combine a second season of GP2, where he drove for Racing Engineering this year, with his Sauber commitments.
"I am really pleased to become a member of the Sauber F1 team, which has a long tradition of building up excellent drivers," said Marciello, who finished eighth in GP2 this season after winning last year's Formula 3 European Championship.
"I really think that this is the best choice for my future career.
"I am also happy to compete for one more season in the GP2 Series, which, together with my new F1 role, will give me a very busy 2015 season."
Team boss Monisha Kaltenborn said Marciello's deal with her Ferrari-powered squad included some appearances in grand prix practice sessions.
"He proved his great talent in junior formulas, and his season in the European Formula 3 Championship with 13 wins and the title victory was particularly impressive," she said.
"We will give Raffaele the opportunity to become familiar with Formula 1, which also includes him taking part in some free practice sessions on Fridays."
Marcus Ericsson and Felipe Nasr form Sauber's race line-up for 2015.