Almost nothing is known about the life and the episcopate of Lazarus, apart that he had a stern appearance and he probably studied in Milan. Probably he, following Pope Leo the Great, took measures against the Manichaeans.
Lazarus died on March 14, 449, and he was buried in the Church of Saint Nazarius and Celsus in Milan. His feast day was anticipated to the February 11 due to the Lent time. A late tradition, with no historical basis, associates Lazarus with the Milan's family of the Beccardi.