Conrad was born and raised in Edgewood, a suburb of Pittsburgh, Pennsylvania, the son of Jim Conrad, an engineer, and Margaret Conrad, a librarian. Growing up the youngest of three boys, he attended the all-boys preparatory school The Kiski School, where he returns from time to time, to visit previous teachers. In fact, David Conrad actually filmed a documentary on one of the most influential teachers he ever had. He went on to attend Brown University, where he studied drama and theater, and later New York’s prestigious Juilliard School. While at Juilliard, Conrad appeared in a stage adaptation of John Irving's novel The Cider House Rules, written by Peter Parnell and co-directed by actor Tom Hulce. Conrad has been teacher of Literature and Drama in Pittsburgh's University for five years.
Conrad made his feature film debut with a small role in the 1994 film Under Heat. In 1996, he won a breakout role as Leo Roth on the television series Relativity; however, he was already committed to a Pittsburgh production of the Tom Stoppard play Arcadia. Because the producers felt Conrad was right for the part, production on the series was later scheduled to accommodate his work on the play. Conrad went on to appear opposite Sigourney Weaver in Snow White: A Tale of Terror (1997), and with Vince Vaughn and Anne Heche in Return to Paradise (1998).
Continuing with his stage career, Conrad made his Broadway debut as Blythe Danner's much younger lover in a revival of Terence Rattigan's The Deep Blue Sea in 1998. He went on to appear in Off Broadway productions of Troilus and Cressida, Richard II and Tom Stoppard's Indian Ink. Most recently, in June 2009, he performed as Pale in the play Burn This at the New Hazlett Theater in Pittsburgh.
In 1999, Conrad appeared in the TV drama The Weekend with Gena Rowlands and Brooke Shields. That same year he appeared in the Hallmark Hall of Fame television movie A Season for Miracles, opposite Carla Gugino. Next, he portrayed a naval lieutenant alongside Robert De Niro and Cuba Gooding, Jr. in Men of Honor (2000) and also appeared in recurring roles on the The WB Television Network series Roswell (1999-2002) and Fox’s dramatic series Boston Public (2000-2005).
In 2003, Conrad appeared in a small role in the Woody Allen comedy Anything Else and was cast as Detective Ed Exley in the network adaptation of L.A. Confidential; though the pilot was not picked up to series, Conrad soon found work on NBC’s Miss Match, in which he tries to win the heart of professional matchmaker Kate Fox (Alicia Silverstone). The series was pulled after airing 11 of 18 episodes.
In 2005, Conrad appeared in the comedy Wedding Crashers with Vince Vaughn and Owen Wilson, as well as landing a regular role on the CBS series Ghost Whisperer, in which he portrays Jennifer Love Hewitt’s paramedic husband, Jim Clancy. When Jim Clancy dies of a gun shot in the series (Season 4), his ghost enters the body of a man named Sam Lucas. Sam was killed in an automobile accident, but Jim's spirit entered the body as soon as Sam's went into the light, therefore reviving the body. Thus, Conrad now plays the roles of Jim and Sam in the series. According to the producers, everyone on the show will start seeing Jim as Jim again.
- Wedding Crashers (2005)
- Ghost Whisperer (2005-present)
- Roswell (2000)
- Snow White: A Tale of Terror (1997)