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.