He was also a regular on the 2006 program Love Monkey.
He also directed two episodes of The Secret Life of the American Teenager: "Slice of Life" and "Just Say No".They appeared on August 26, 2008 and September 9, 2008 on ABC Family.On July 15, 2007 he returned to series television as one of the lead males in Lifetime Television's comedy-drama Side Order of Life. He is best known as the virtuous Brandon Walsh on the television series Beverly Hills, 90210 and for his role starring as Richard "Fitz" Fitzpatrick in the show Call Me Fitz.Priestley first started his television career doing commercials for companies such as Fletcher's Meats and then guest-starring as Bobby Conrad a.k.a.
Roberto Coronado Jr., a mobster's grandson, in the early 1987 episode "A Piece of Cake" from the final 4th season of the television series Airwolf, and appeared in two episodes of 21 Jump Street in 1987–88, then moved on to the 1989 short-lived sitcom Sister Kate which starred Stephanie Beacham.
He played Todd, one of the fosterchildren under the care of Sister Kate, an English nun.
In 1990, Priestley was chosen as Brandon Walsh on the hit series Beverly Hills, 90210.
The show garnered worldwide fame and made Priestley a teen idol, he was nominated for two Golden Globes for his work on the show. He remained on the show until 1998, when Brandon moved to Washington, DC.
Brandon was the last Walsh to leave the show; however, Priestley would continue to serve as an executive producer until the show ended in 2000.
Priestley joined the cast of Tru Calling as Jack Harper from 2004–05.