Lancellotto received his early education in Castronuovo and later studied in Venice and Naples. He was ordained a priest at the age of twenty-six and initially practiced Canon Law in the ecclesiastical courts. However, a small lie he told during an argument led him to deep remorse, prompting him to renounce his legal profession.
He was inspired by the words, “The mouth that lieth, killeth the soul,” from the Scriptures. This experience led him to dedicate himself to the sacred ministry and eventually join the Theatine Order in 1556, taking the name Andrew.
As a Theatine, St. Andrew Avellino became known for his virtues and dedication. He was made Master of Novices and later oversaw several houses within the Order. He imposed upon himself additional vows, including working against his own inclinations and striving for continuous perfection. He was known for his fervent love for God and spent much time in prayer and working for the salvation of souls. He was also a friend of St. Charles Borromeo, who sought his advice on Church matters.
St. Andrew was known for his piety and was said to have experienced miracles. One such instance involved a heavenly light guiding him and a companion during a storm when they were carrying the Viaticum. He also had visions and the gift of prophecy. He was deeply devoted to the Passion and death of Jesus Christ and the Blessed Sacrament.
St. Andrew Avellino is the patron saint against sudden death. This is due to the circumstances of his death. On November 10, 1608, at the age of eighty-eight, he was preparing to celebrate Mass when he suffered a stroke and died.
He is also a patron saint of Naples and Sicily.