Growing up in San Diego, becoming an actor came naturally to Dana Ashbrook. His father is the director of the Palomar College Department of Performing Arts, and his mother is a teacher who performs in local theater. His sisters, Daphne Ashbrook and Taylor Ashbrook, are also working actresses. His own career started while still in his teens, when his sister Daphne's agent saw him performing in a high school play, and he made a good impression. He started out with guest appearances in TV series, and then went on to supporting roles in motion pictures. His big break was winning the role of "Bobby Briggs" in the offbeat television series Twin Peaks. His shaggy hair, soulful appearance, and intense portrayal of the volatile school athlete made an impression. After the show went off the air, he continued to make appearances in television and film. In 1997, he won a starring role in the series Crisis Center, but in spite of its promise, the series only lasted one season. He made a comeback when he was cast in a recurring role in the popular teen soap opera Dawson's Creek.

In his spare time, he plays basketball and tennis. He is also an accomplished harmonica player.
Brother of writer Taylor Ashbrook and actress Daphne Ashbrook. Is friends with Kimmy Robertson. Graduated high school in 1985. Got his SAG card when he appeared in the 1986 episode of Cagney & Lacey. Wrote a road movie script called "Driven To It" with friend Robert Bauer that David Lynch offered to executive produce (in name only) in order to help them, but Ashbrook and Bauer couldn't get financing for it. Created with Robert Bauer a film company called Bauerbrook Films.