After moving to Los Angeles in the 1960s, the 20-year-old twins were discovered by Actress Loretta Young in 1962 and cast in her CBS series, The New Loretta Young Show. On 5 February 1967, Dirk Rambo was killed in a road accident at the age of 25.

Later that same year, Dack Rambo landed the role of Jeff Sonnett on The Guns of Will Sonnett, and co-starred in the short-lived Gunsmoke spin-off, Dirty Sally, with Jeanette Nolan. During the 1970s and 1980s, he made guest appearances on Marcus Welby, M.D., House Calls, Wonder Woman, Charlie's Angels, All My Children, Fantasy Island, The Love Boat, Hotel and Murder, She Wrote. He also acted out the lead role in Sword of Justice, which lasted for ten installments in 1978-79. Rambo may be best remembered on television for playing Jack Ewing in 51 episodes of the soap opera Dallas from 1985-87, although over 60% of the Dallas episodes that Rambo appeared in ended up being explained away as a dream that the character Pamela Barnes Ewing had been having. Rambo also played Wesley Harper on the 1984 short lived TV series soap opera Paper Dolls.

While working on Another World, Rambo learned that he was infected with HIV in August 1991. He quit the series shortly thereafter and retired from acting. Rambo then publicly announced that he was HIV positive and that he was bisexual, revealing that he had been in a lot of relationships with both men and women since his 20s.

Dack Rambo died on 21 March 1994 at the age of 52, of complications from AIDS.

Norman Jay Rambo (aka Dack Rambo) was born in Earlimart, California, to william Lester Rambo (aka Lester Rambo – 1904–1987) and Beatrice A. Rambo (nėe Rossi – 1910–2002). He had an older brother, william Donald Rambo (aka Bill Rambo – 1933–2011); an identical twin brother, Orman Ray Rambo (aka Dirk Rambo – 1941-1967); and a younger sister, Beverly Rambo (born 1944). Beatrice Rambo outlived two of her three sons.