LOS ANGELES, July 27 (UPI) -- Eric Christian Olsen is joining "NCIS: Los Angeles" as a series regular this season, CBS announced Tuesday.

Olsen guest-starred on the show last season as Los Angeles Police Detective Liaison Marty Deeks.

Deeks, a seasoned LAPD undercover detective, was recruited to the NCIS team by Operations Manager Hetty Lange, played by Linda Hunt, the network noted.

Olsen will begin reprising his role as Deeks in the drama's special 2-hour Season 2 premiere Sept. 21.

"We are thrilled to have Eric join the cast," Executive Producer Shane Brennan said in a statement. "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."