Singer captured the World Lightweight Championship in July, 1930, with a first round knockout (1:47) of champion Sammy Mandell. He surrendered the title four months later to Tony Canzoneri in a first round KO. Three years earlier, Singer and Canzoneri had battled to a 10-round draw. In his career, Singer won 61 of 72 pro fights (25 by KO), drawing twice, and losing nine.