Hartman attended California State University, Northridge, where he graduated with a degree in graphic arts. After his graduation, he designed album covers for numerous bands including Poco and America. In 1975, he joined the comedy group called The Groundlings. There he helped comedian Paul Reubens to develop his character named Pee-wee Herman.
Hartman made his movie debut in a 1980 American comedy film The Gong Show Movie, which was directed by Chuck Barris. The movie grossed $6,621,520 at the box office. After a couple of years, he featured in a comedy film Pandemonium, which was directed by Alfred Sole. The co-stars of this movie are Carol Kane, Judge Reinhold, Tom Smothers, and Eileen Brennan.
In 1993, Hartman featured in an American satirical comedy film Loaded Weapon 1, which was directed by Gene Quintano. The co-stars of this movie are Emilio Estevez, Jon Lovitz, Tim Curry, and William Shatner. The movie became a huge hit and grossed $28 million at the box office against the budget of $8.2 million.
Later, Hartman appeared in an American science fiction/fantasy action comedy movie of Joe Dante called Small Soldiers. The cast members of this movie are Kirsten Dunst, Kevin Dunn, Denis Leary, and Frank Langella. The total budget for this movie was $40 million and grossed $71.1 million at the box office.
Hartman has been also featured in numerous movies and television series that includes Cheech & Chong's Next Movie, Last Resort, Three Amigos!, Coneheads, The Pagemaster, Stuart Saves His Family, Buster & Chauncey's Silent Night, The Pee-wee Herman Show, Challenge of the GoBots, Pee-wee's Playhouse, Eek! The Cat, The Ren & Stimpy Show, 3rd Rock from the Sun, and Happily Ever After Fairy Tales for Every Child.
Hartman was American by nationality. He was married to his girlfriend Gretchen Lewis in 1970. However, the couple was unable to continue their married life and they got divorced. After his divorce from his first wife, he married real estate agent Lisa Strain in 1982 and they lived together for three years. In November 1987, he married Brynn Omdahl, a former model, and aspiring actress. The couple together had two children, Sean and Birgen Hartman.
As an actor and comedian, Hartman earned a huge amount of money from his professional acting career. He has been featured in numerous movies and television series from which he must have collected a decent amount of salary. Before he died his net worth was $2 million.