His parents is Alan Roger Ackles, an actor, and Donna Joan Shaffer. Jensen has an older brother, Joshua, and a younger sister, Mackenzie, and is of Irish, English, and Scottish ancestry.
In school he playd baseball and lacrosse. He planned to study sports medicine at Texas Tech University and become a physical therapist before moving to Los Angeles to become an actor. He started modeling, Ackles began to concentrate on an acting career in 1996. He appeared in several guest roles on Mr. Rhodes, Sweet Valley High, and Cybill before joining the cast of the NBC soap opera Days of Our Lives as Eric Brady in 1997.
He won a 1998 Soap Opera Digest Award for Best Male Newcomer and went on to be nominated three times (in 1998, 1999, and 2000) for a Daytime Emmy Award for Outstanding Younger Actor in a Drama Series for his work on Days of Our Lives.
Ackles departed Days of Our Lives in 2000 and went on to appear in the mini-series Blonde about the life of Marilyn Monroe. He also auditioned for the role as the young Clark Kent on Smallville, but it was offered to actor Tom Welling instead. After failing to land the part, he appeared in a guest role on the James Cameron television series Dark Angel on Fox during its first season in 2001 as Ben, the psychopathic, serial killer "brother" of the main character that was played by Jessica Alba. His character died in the episode, but Ackles returned to the show as a series regular in the second season as Ben's twin, Alec. He remained with the show until its cancellation in 2002.
Ackles worked steadily throughout 2003. He joined the cast of the WB's hit show Dawson's Creek during the final season, playing C.J., Jen Lindley's lover. Jensen filmed several episodes of the unaired series Still Life for Fox before it was abruptly dropped. He also had a small role in the 2004 short film The Plight of Clownana.
In 2004 to become a regular on Smallville , playing Jason Teague, the romantic interest of Lana Lang, played by Kristin Kreuk. He also had a lead role in the 2005 film Devour, where his father also had a role.
Most recently, Ackles joined the cast of the WB horror series Supernatural in 2005, where he co-stars as Dean Winchester. Dean teams with his brother Sam (Jared Padalecki) to road-trip across the country investigating the paranormal while searching for their missing father, John Winchester (Jeffrey Dean Morgan). The second season was picked up by The CW in 2006 for the 2006-2007 television season. In 2007 Jenen was cast in the movie Ten Inch Hero, which he plays Priestly.