He was one of the first bandleaders to integrate his band; the year is variously given as 1935 or 1937. He was an outspoken admirer of Count Basie and Duke Ellington; Ellington once lent Barnet his charts after Barnet's had been destroyed in a fire. Throughout his career he was an opponent of syrupy arrangements.
Barnet was at the height of his popularity between1939 and 1941, a period that began with his hit "Cherokee." In 1944 he had another big hit with "Skyliner". In 1947 he started to switch from swing to bop. During his swing period his band included Buddy DeFranco, Roy Eldridge, Neal Hefti, Lena Horne, Barney Kessel, Dodo Marmorosa and Oscar Pettiford, while later versions of the band included Maynard Ferguson, Doc Severinsen, and Clark Terry.
In 1949 he retired, apparently because he had lost interest in music; he was able to retire so young because he had been born wealthy. He occasionally returned from retirement for brief tours but never returned to music full time.