Joseph Mahfouz joined the Congregation of the OLM and received on 29 June, 1960, the ordination to the priesthood.
Pope John Paul II appointed him on June 9, 1990, Archbishop of the Eparchy of the Our Lady of Lebanon in São Paulo.
Maronite Patriarch of Antioch, Nasrallah Boutros Sfeir gave him on 12 August of the same year the episcopal ordination.
Mahfouz resigned as Bishop of Our Lady of Lebanon in São Paulo on 14 October, 2006.
He died of cancer and was buried in the cemetery Nisbei Ghosta in Lebanon.