He began working as a professional musician in 1931. In 1939 he organized his own big band, which later featured Charlie Parker, Bernard Anderson, and Walter Brown. Although its book included both swing and blues numbers, the band played blues on most of its records; its most popular recording was "Confessin' The Blues". The group disbanded when McShann was drafted in 1944, but re-formed when he was discharged the same year.
Sometime in the later 1940s McShann started to lead small groups featuring Jimmy Witherspoon; Witherspoon started recording with McShann in 1945. McShann then played in obscurity until 1969, when he became popular as a singer as well as a pianist, often performing with Claude Williams. He continued recording and touring until the mid-1990s.