Hambleton began his Broadway producing career in 1937 with Robin Landing. He produced five other shows before co-founding with Norris Houghton the influential Phoenix Theater in 1953. Over the next three decades, the company supported numerous renowned artists--both behind the scenes such as Wendy Wasserstein, Jerome Robbins and Marsha Norman and on the stage Meryl Streep, Jessica Tandy, Uta Hagen and more. The company produced many Broadway productions, often staging them in repertory. During this period Hambleton without the Phoenix produced the original production of Once Upon a Mattress. In 1968 APA-Phoenix Repertory Company the company into which the original Phoenix Theater had evolved won a special Tony Award. Hambleton was head of the company until it closed in the early 1980s because of funding issues. In 2000 he received a Special Lifetime Achievement Tony Award. The recently established T Fellowship at Columbia University, which aims at supporting and developing emerging theatrical producers, is named after Hambleton.