The new deal will keep the 21-year-old at the Veltins-Arena until the summer of 2013.
Unnerstall is currently back-up to Ralf Fahrmann at Schalke.
Schalke general manager Horst Heldt told his club’s official website: “Lars Unnerstall has agreed a new contract with our club, he has signed new terms.
“We are delighted with the progress Lars Unnerstall has been making in the past couple of seasons. Lars Unnerstall is a young goalkeeper with potential.”
