He was bour in Los Angeles, California, USA. He was attended St. Joseph's Catholic school and Los Angeles High School.He was graduated from law school, passed the California bar and was a practicing criminal defense attorney for a short time before entering the movie business. He was pressured by his father to study law at USC. He was a brother of director Ray McCarey. He and his wife Stella lived at 1014 North Crescent Drive in Beverly Hills, two blocks away from McCarey's friend and fellow filmmaker Hal Roach.
He was a practicing criminal defense attorney for a short time in Los Angeles and San Francisco. McCarey often told a story about his last case when he was conned into defending a wife-beater, who chased him out of court and down the street. That incident was the conclusion of his legal career. McCarey would later claim that he never won a single case.
According to director Edward Dmytryk, who worked for him as an editor, McCarey never forgot a slight. He once told Dmytryk that early in his career Paramount had humiliated him by unceremoniously throwing him off the lot the moment a picture he was making for them was completed. After he became successful Paramount hired him for several more pictures, but McCarey got his revenge, he told Dmytryk, because "every picture I make for Paramount costs them a half-million more than it should".