Born on November 8, 1961 in Hollywood, California, Leif grew up in a world of showbiz and got his first taste of acting in the blockbuster film, Bob & Carol & Ted & Alice (1969) playing the son of Elliott Gould and Dyan Cannon, though he was uncredited. Then he was a frequent guest in TV shows such as "Nanny and the Professor" (1970), "Family Affair" (1966), "Cannon" (1971), "Gunsmoke" (1955) and "The Odd Couple" (1970) as well as receiving brief exposure in Walking Tall (1973) and Peopletoys (1974), both films also starring his sister, Dawn Lyn. He then played Endy Karras in the TV series "Three for the Road" (1975), also starring Alex Rocco and Vincent Van Patten, and by then he started getting exposure on teen magazines and fan mail, despite the show's short run. He still pursued his acting career by starring in some westerns like Diamante Lobo (1975), Vengeance (1977) and Peter Lundy and the Medicine Hat Stallion (1977) (TV).
However, by then he wanted to be a singer and Michael Lloyd, who was producing records for Shaun Cassidy at the time, signed him up as well. He released two oldie cover singles "Surfin USA" and "Runaround Sue" as well as his self titled debut album, but wasn't really happy with this style of music. He recorded another album called "Feel the Need" which had a top 10 disco flavoured hit his producer wrote called, "I Was Made for Dancin'". He released 3 more albums and walked away from music.
He continued in films and was well remembered for his small supporting role in the Blockbuster film The Outsiders (1983), which starred Matt Dillon, Patrick Swayze, Rob Lowe, Emilio Estevez and Tom Cruise, but his films after that were not very successful. However, he did return to music by playing in a band called "Godspeed", as this time he's playing his own music.