Thelma Hill was born Thelma Floy Hillerman in Emporia, Kansas. Her family moved to Los Angeles, California during her early teen years. She became one of the star-struck, wide-eyed girls who hung out near the Mack Sennett studio, peering through the gates. It took her five years, but eventually, using her womanly wiles, she weaseled her way through the gates and quickly caught the eye of Sennett himself and F. Richard "Dick" Jones, a producer and director who would work with Thelma in over a dozen films.
Thelma did bit parts and extra work throughout her school years, working weekends and during vacations. Because of her youth, beauty, and spunk, she quickly became "everybody's protégé."