Eric Christian Olsen Eric Christian Olsen

NCIS: Los Angeles has upgraded Eric Christian Olsen to a series regular for the show's second season, CBS announced Tuesday.

Last season, Olsen recurred as Marty Deeks, a seasoned LAPD undercover detective who was recruited to the NCIS team. He'll appear in the two-hour season premiere.

Check out photos of the NCIS: Los Angeles cast

"We are thrilled to have Eric join the cast," executive producer Shane Brennan said.  "He has already proved himself to be a great asset and invaluable member of the team, and Eric's fans will be delighted to see what we have in store for him."Olsen has previously appeared on Tru Calling, Brothers & Sisters, and Community. NCIS: Los Angeles returns Tuesday, Sept. 21 at 9/8c.