Oakland was married to Lois Lorraine Porta (1918–2003). The couple had one daughter, Barbara.

Oakland was born in the Brooklyn borough of New York City, the son of a plasterer and builder Jacob Weiss and his wife Ethel Oaklander. While he later claimed in media interviews to have been born in 1922 (a date repeated in his New York Times obituary), Social Security and death indexes indicate he was born Simon Weiss in 1915; his stage name was likely derived from his mother's maiden name, Oaklander.

He began his performing arts career as a musician (he was a Violinist, an avocation he would pursue during his entire career as an actor). Oakland began his acting career in the late 1940s. He enjoyed a series of Broadway hits, including Light Up the Sky, The Shrike and Inherit the Wind, and theater was one of his lasting passions. He was a concert Violinist until the 1940s.

In 1955 Oakland made his film debut, though uncredited, as an Indiana state trooper in The Desperate Hours. He next appeared in two films released in 1958: as the character Mavrayek in The Brothers Karamazov and then in the role of Edward Montgomery in I Want to Live! The character Montgomery was a real-life Journalist, who had reported on the California murder trial and 1955 execution of Barbara Graham, played by Susan Hayward in the film. Oakland's portrayal of the Journalist as a "tough, but compassionate" personality resulted in the actor's often being typecast in his subsequent roles in both films and on television.

Simon Oakland continued working up to the year of his death. His last credited acting appearance was ironically in the episode "Living and Presumed Dead" on the CBS television series Tucker's Witch. That episode aired just three months before Oakland died of colon cancer in Cathedral City, California, on August 29, 1983, a day after the actor's 68th birthday.