Thornton was placed on the injured list on Oct. 7 because of swelling in his surgically repaired right knee. Thornton missed more than three weeks but will return Tuesday night when San Jose hosts the New York Rangers.
Thornton, 39, is coming off his second straight year undergoing reconstructive knee surgery. He played the first two games for the Sharks and has one assist.
Forward Dylan Gambrell was reassigned to the AHL to make room for Thornton.