Born to a Jewish family in New York, he began his acting career at the Pasadena Playhouse in Pasadena, California. He then spent several years in theater groups before moving on to Broadway and, eventually, Hollywood. In 1939, he signed with Warner Brothers and was cast in supporting roles, many times along with James Cagney, in such movies as Cagney's Yankee Doodle Dandy (1942), as well as with Gary Cooper in Sergeant York (1941) and Irving Berlin, Ronald Reagan, and George Murphy in This Is The Army (1943).
In 1954, Actress Lynn Baggett was involved in a collision in Los Angeles while driving a car borrowed from Tobias, and a 9-year-old boy was killed. (Baggett and Tobias were old friends, and she reportedly had been his girlfriend in the 1940s, but at the time of the accident she was the estranged wife of Producer Sam Spiegel.) She eventually was acquitted of manslaughter but convicted of felony hit-and-run, and she spent 55 days in jail. The boy's mother sued Baggett and Tobias in separate court proceedings. They shared responsibility for damages, which amounted to $2,599.
From 1959 to 1961, Tobias played Penrose in eight episodes of the ABC television series, Adventures in Paradise, starring Gardner McKay. From 1964 to 1971, he played Abner Kravitz, the long-suffering neighbor on the ABC sitcom Bewitched. Tobias often appeared in an uncredited role as a courtroom spectator on the CBS program Perry Mason, and he played Sidney Falconer in the episode titled "The Case of the Antic Angel" (1964).
Tobias never married and retired from acting in 1977 after reprising his role as Abner Kravitz in a guest appearance on the Bewitched sequel Tabitha.
On February 27, 1980, Tobias died of bladder cancer at the age of 78 at Cedars Sinai Medical Center in Los Angeles. He is buried in Mount Carmel Cemetery, Glendale, Queens, New York City.
