After becoming an actor, he worked in Broadway plays and in touring theatrical companies for many years prior to his 1930 movie debut.

He featured with Donald Meek in a series of short mysteries based on S.S. Van Dine stories for Warner Brothers.

He played various types of characters, but most often figures of authority like judges and lawyers, politicians and commissioners, doctors and military officers.

Among other roles, Hamilton appeared as a judge who passes sentence on soon-to-be-racketeer James Cagney for violation of the Volstead Act in The Roaring Twenties (1939).

Hamilton also appeared as a police inspector in the John Huston film In This Our Life in 1942, and got several lines as DA Bryan quizzing Humphrey Bogart's Sam Spade in The Maltese Falcon (1941).