Schlesinger was born to a Jewish family in Philadelphia. After working at a theater as an usher, songbook agent, actor, and manager (including the Palace Theater in Buffalo, New York), he founded Pacific Title & Art Studio in 1919, where most of his business was producing title cards for silent films. As talking pictures (“talkies”) replaced them in 1929 and 1930, Schlesinger looked for ways to capitalize on the new technology and stay in business. Some film historians, like Tom Sito, claim that he helped finance the Warner Brothers’ first talkie, The Jazz Singer (1927). He then secured a contract with the studio to produce its brand-new Looney Tunes series, and he signed animators Hugh Harman and Rudy Ising to create these cartoons with their Bosko character as the star.

Schlesinger was a shrewd businessman with a keen eye for talent. When Harman and Ising left Warner Bros. with Bosko in 1934, Schlesinger set up his own studio on the Warner Bros. Sunset Boulevard lot at the corner of Van Ness and Fernwood. He wooed animators away from other studios, including some of those who had departed with Harman and Ising including Bob Clampett. One of these was Friz Freleng, whom Schlesinger promoted to oversee production of Looney Tunes and to develop the sister series, Merrie Melodies. Freleng’s talent quickly shone through, and Schlesinger’s hiring of Robert McKimson, Tex Avery, Chuck Jones and Frank Tashlin further increased the quality of the studio’s output. He later added Carl Stalling and Mel Blanc, and collectively these men created such famous characters as Porky Pig, Daffy Duck and Bugs Bunny. Schlesinger largely took a “hands off” approach to the animation unit, allowing his directors freedom to create what they wished, provided that the resulting films were successful. Schlesinger sold Pacific Title & Art Studio in 1935 to concentrate on his animation studio.

Schlesinger remained head of the animation studio until 1944 when he sold his assets to Warner Bros. He continued to market the characters and headed Warners’s Theater Services unit until his death from a viral infection on Christmas Day, 1949 at the age of 65.