Priestley started out making commercials and working as a child actor in his native Canada, before moving to Los Angeles in 1987. After guest appearances on popular shows such as 21 Jump Street, MacGyver, and Quantum Leap, Priestley landed a recurring role as an orphan on the short-lived sitcom Sister Kate in 1989. It was his next acting gig that led to a career breakthrough. In the fall of 1990, Priestley starred in Beverly Hills, 90210—a primetime drama created by super producer Aaron Spelling. He played Brandon Walsh, a wholesome teenager who moves to Beverly Hills from Minnesota with his parents and twin sister Brenda, played by Shannen Doherty.
Audiences delighted in taking a fictional look at the happenings at West Beverly High School—the hook-ups, the break-ups, the fights, and the friendships. During the show’s run, it tackled numerous issues, such as sex, peer pressure, drinking, and drug abuse. With the role of Brandon Walsh, Priestley became the object of great admiration by fans. In 1993, he earned his first Golden Globe nomination for Best Performance by an Actor in a Television Series – Drama for his portrayal of Brandon. Brandon Walsh, with his fairly solid moral compass, served as a role model for many of the show’s young viewers. He was nominated for the same award in 1995.
While on the series, Priestley appeared in several movies, including Tombstone (1993), Calendar Girl (1993), and Love and Death on Long Island (1997) with John Hurt, which received mostly positive reviews. Priestley also tried his hand at directing, taking the reins of several episodes of Beverly Hills, 90210 and several music videos, including the one for the song “The Old Apartment” by the Canadian band Barenaked Ladies in 1996. Priestley left the show in 1998 to pursue other opportunities. In 1999 he appeared in the cable television movie, Kiss Tomorrow Goodbye, which he also directed and executive produced. Priestley also directed a documentary about the band Barenaked Ladies entitled Barenaked in America. In 2000, Priestley appeared on stage in the London production of Side Man, the Tony Award-winning play by Warren Leight. Priestley played Clifford, the son of a jazz musician and an alcoholic. Edie Falco of The Sopranos fame played his mother.
That same year he returned to his old television stomping grounds—Beverly Hills, 90210—for the series finale. Besides acting, Priestley pursued a career as a race car driver. In August 2002, he was seriously injured in a crash at the Kentucky Speedway in Sparta, Kentucky. His racecar hit two walls during a practice session after running across a patch of oil dry, a material used to soak up fluids after an early spill on the track. Priestley suffered a broken back and other injuries as a result of the crash. After intensive treatment and physical rehabilitation, he was able to recover from his injuries. He has since retired from racing. Priestley made a return to television with the dark drama Tru Calling in 2004, which was cancelled in 2005. His 2006 television series, Love Monkey, was short-lived, lasting for only eight episodes despite earning strong reviews. Priestley has also appeared in several independent films, including Die, Mommy, Die! (2003), a dark comedy.
- She Came in Through the Bathroom Window • Must Be a Guy Thing • Angels We Have Heard on High • Fade In, Fade Out • Bleeding Hearts
In December 1999, Priestley was involved in a car accident and was charged with drunk driving. He pled no contest to a misdemeanor drunk driving charge and was sentenced to spend five nights in a detention facility in Los Angeles and to attend a drug and alcohol abuse treatment program. Priestley lives in Los Angeles with his wife, Naomi. The couple married in 2005. His first marriage to Ashlee Petersen was brief; the couple married in 1998 and divorced about a year later.
- Twin brother of actress Justine Priestley.
- Chosen by People magazine as one of the 50 Most Beautiful People in the world. 
- Chosen by People magazine as one of the 50 Most Beautiful People in the World. 
- Plays hockey.
- Priestley won a 1998 Grand-Am race at the Mid- Ohio Sports Car Course.
- He was seriously injured in a practice run of a car race at the 2002 Kentucky Speedway when his automobile crashed into a wall. The car slammed into the wall at nearly 290 km/h, and as a result, he sustained such injuries as a fractured spine, broken bones, and concussion.
- Ranked #11 in TV Guide's list of "TV's 25 Greatest Teen Idols" (23 January 2005 issue).
- His favorite band is Siouxsie and the Banshees.
- Narrator for Movie Central channel filmographies for various Canadian actors.
- His former "Beverly Hills, 90210" (1990) co-stars Jennie Garth, Tori Spelling, Tiffani Thiessen, and Ian Ziering were among the guests at his wedding to Naomi Lowde-Priestley.
- Was among the guests at Tiffani Thiessen's wedding to Brady Smith.
- Jason and Naomi became the parents of a baby girl, Ava Veronica Priestley, born July 2, 2007.
- A son, Dashiell Orson Priestley, was born July 9, 2009.