Brian Dietzen is an American actor who has played the supporting role of Dr. Jimmy Palmer on NCIS since 2004. In 2012, he was promoted to a series regular at the beginning of the show's tenth season.

Dietzen moved to Colorado when he was young.^[1] He first started acting in elementary school plays.^[2] Later, he studied theatre at the University of Colorado at Boulder's Bachelor of Fine Arts program.^[3]

Dietzen has appeared in productions of Equus and Waiting for Godot and joined The Colorado Shakespeare Festival for two years. He was cast in The WB series My Guide to Becoming a Rockstar. The part was a series regular as the drummer of the group. He later teamed up with John Riggi for a two-man show with Steve Rudnick called The Oldest Man in Show Biz.

He performed in the film From Justin to Kelly and has had a recurring role as Dr. Jimmy Palmer, a medical examiner's assistant, later Chief Medical Examiner on the CBS series NCIS, since the first season episode, "Split Decision". Starting in season 10, he is a regular cast member with Dietzen also appearing in the opening credits.

He suffered a stroke in 2020 but recovered well from it. He also had cardiac surgery that same year.^[4]