Reed Diamond was born on July 20, 1967 in New York City, where he was raised as the son of Allison, an astrologer and Bob, a director. He was educated at University of North Carolina at Chapel Hill and moved on to training to become a police officer before he ventured into studying acting at Juilliard School.
During the 1990s, Reed Diamond had roles in Boy Meets Girl, Assassins, Clear and Present Danger, and on several episodes of Class of ’96. After portraying characters on several TV movies, he was seen on an episode of Mighty Ducks and played Detective Mike Kellerman on Homicide: Life on the Street. He reprised this role in the telefilm Homicide: The Movie. In 2001, Reed Diamond got a part in Madison, and was also seen on three episodes of The Huntress. He was also in Family Law, Presidio Med, The Twilight Zone and The Shield, where he was promoted to main cast member eventually. Diamond later got the role of Stuart Collins in Judging Amy, and played Algernon in the 2004 blockbuster, Spider-Man 2. Also that year, he appeared in Crossing Jordan and on episodes of The West Wing. In 2005, Diamond was cast in Medium, Good Night and Good Luck, CSI: Crime Scene Investigation, Law & Order and Numb3rs. The next year, he was a guest star on Stargate SG-1, Without a Trace, Vanished and CBS’ Ghost Whisperer. In 2007, Reed Diamond joined the cast of the NBC series Journeyman as the character Jack Vasser. He played the brother of the lead character, played by Kevin McKidd. When the show was cancelled in December of 2007, the actor decided to pursue other projects. Diamond later found himself filming Criminal Minds, as well as taking on the role of Laurence Dominic on the series Dollhouse.