In 1941 Powell was elected as a Democrat to the New York City Council and the following year founded the People's Voice. Elected to the House of Representatives in 1945 he was chairman of the House Committee on Education and Labor from 1951 but was subject to persistent absenteeism which inhibited his effectiveness. Powell was the first recorded user of the phrase Black Power (at Harvard in 1966) and acted as the first convenor of the National Conference on Black Power.
In 1967, Powell was expelled from the House of Representatives for misusing public funds and for unbecoming conduct. Re-elected to the House in 1968 he won a Supreme Court ruling in his favor of his appeal against expulsion. Powell lost his seat in 1970.