As an actor, he starred in the 1970s as a young resident, Dr. Paul Hunter, on The Bold Ones: The New Doctors and as a teacher in the series Lucas Tanner.

After working in films such as the Doris Day comedyThe Ballad of Josie (1967), Nobody's Perfect (1968), and Did You Hear the One About the Traveling Saleslady?

Hartman played a lead role alongside Hal Linden in the industrial musical Diesel Dazzle (1966).

"[4] In a statement that Hartman prepared for the 30th anniversary GMA broadcast in 2005, he explained, "My daily sign-off line, 'Make it a good day today,' reflected 'GMA's' values and the belief that each of us can affect our lives in a positive way, that our program was, we hoped, a public service.

"[5] Hartman has been an anchor and host of a series of documentaries on the Discovery Channel and PBS member station WNET in New York City.