One of the top male vocalists of the late 1930s, Jack Leonard was rivaled only by Bing Crosby in popularity. Leonard was working in Bert Block's orchestra in 1935 when Tommy Dorsey hired him away. Dorsey also took trumpeter Joe Bauer and arranger Axel Stordahl, then known as Odd Stordahl. Together the men formed a vocal group call the Three Esquires. It was as a soloist, though, that Leonard would achieve stardom, singing on such classics as ''Marie,'' ''All the Things You Are,'' ''Our Love,'' and ''Indian Summer.''
Leonard was a shy, handsome man who was liked by all. He was very near-sighted but refused to wear glasses in public so as not to spoil his romantic image. His departure from Dorsey's orchestra in November of 1939 was a surprise to his bandmates. The rumor was that Dorsey had grown suspicious of Leonard's intentions, fearing that he was going to leave soon for a solo career, and had forced him out, though Leonard himself tried to dispel it at the time, saying he just needed a break and would return soon. He never did. He was replaced in the band by Alan DeWitt, who failed to work out and was replaced after only one month by Frank Sinatra.
Leonard continued singing professionally throughout the 1940s and at least into the 1950s, though he never achieved the level of recognition as a solo artist that he had as a band vocalist. He had appeared in a few uncredited film roles in the 1930s, and in the late 1940s he returned to the silver screen three more times. He also hosted his own television program in 1949 and appeared as one of the hosts for Broadway Open House in 1951. In 1956 he performed at the memorial concert in tribute to Dorsey. Jack Leonard died from cancer in 1988.