Mzali was born in Monastir, Tunisia in 1925. His descends from a family whose ancestor came from the Ait Mzal tribe, a Masmouda clan from the Sous who established the Hafsid dynasty in Tunisia in the 13th-century. His ancestors settled in Tunisia after coming back from the Haj in the late 17th-century.
Mzali fled to France and was replaced by Rachid Sfar. Mzali wrote many books, one of them untitled "Un Premier ministre de Bourguiba témoigne". He served as a member of the International Olympic Committee from 1965 until his death.