Brian Thomsen was a founding editor of the Questar Science Fiction line of books, and served as managing fiction editor at TSR, Inc.; he also wrote over 30 short stories, and collaborated with Julius Schwartz on Schwartz's autobiography. He also worked as the publisher for TSR's Periodicals Department at one point. He was a consulting editor at Tor Books; as an author he was a Hugo Award nominee.

He died on September 21, 2008, at his home in Brooklyn at the age of 49. He was survived by his wife, Donna.