Gained entry into the theatrical world by becoming an influential reviewer for the NY Evening Post, then became a manager for several important stage stars in the 1890's, most notably Julia Marlowe. He became a Broadway producer in late 1902, and scored his first moderate hit with the 1903 production, "Her Own Way," which ran for 107 performances. He enjoyed major hits with musical comedies "Stepping Stones" (1923; which ran for 281 performances at the Globe Theatre) and "Sunny" starring Marylin Miller (running for 517 performances at The New Amsterdam Theatre). With A.L. Erlanger, Dillingham was a partner in the Diller Theatre Corporation (which leased the Fulton Theater) and continued to be a major Broadway producer virtually until his death on August 30, 1934 at age 66.