A veteran of the Yiddish Art Theater from his teens,[1] Harris made his first Broadway appearance in 1937 in Schoolhouse on the Lot.

[3] From 1950 on, he appeared extensively on television series, specializing in playing shady, if not outright evil characters, roles for which he excelled.

He also appeared in other television series such as Peter Gunn, 77 Sunset Strip, Gunsmoke, Ben Casey, The Asphalt Jungle, and Rawhide.

Robert H. Harris also appeared in the first season of Barnaby Jones; episode titled, "Twenty Million Alibis"(May 6, 1973).

His other film credits included roles in Bundle of Joy (1956), The Invisible Boy (1957), Peyton Place (1957), The George Raft Story (1961), Apache Uprising (1965), Valley of the Dolls (1967), How Awful About Allan (1970), The Great Northfield Minnesota Raid (1972) and The Man in the Glass Booth (1975).