Bishop John S. Bonnici was born on February 17, 1965, in New York City, to the late John C. Bonnici and Gertrude (née Rilling) Bonnici. He has one sister.
Bishop Bonnici graduated from the Cathedral Preparatory School and Seminary in Manhattan in 1983, and chose to continue his education at St. John’s University in Brooklyn, New York, where he graduated with a bachelor’s degree in biology and philosophy in 1987. During this time, he began to seriously discern a priestly vocation, and he applied to be a seminarian for the Archdiocese of New York.
Bishop Bonnici began his theological studies later that year at the Pontifical North American College in Rome, with academic studies at the Pontifical Gregorian University, where he earned his Bachelor of Sacred Theology in 1990. He pursued his graduate studies at the Pontifical John Paul II Institute in Rome where he earned his Licentiate of Sacred Theology degree (1990-1992).
Bishop Bonnici was ordained to the sacred priesthood at St. Patrick’s Cathedral in Manhattan on June 22, 1991, the Feast of Sts. John Fisher and Thomas More, by Cardinal John O’Connor for the Archdiocese of New York.
Upon returning from Rome to the Archdiocese of New York in 1992, Bishop Bonnici was assigned to Our Lady of Mount Carmel Parish in Elmsford, New York, to serve as its parochial vicar for two years until his assignment as a faculty member of St. Joseph’s Seminary in Yonkers, New York. Over the course of 20 years, he has served as an adjunct professor of moral theology at St. Joseph’s. In 1994, Bishop Bonnici was assigned to continue his education at the Pontifical John Paul II Institute in Washington, D.C., where he earned the degree of Doctor of Sacred Theology in 1995.
Upon completing his studies, Bishop Bonnici became the assistant director of the Archdiocesan Family Life/Respect Life Office, and the office’s director the following year. His education and pastoral experiences enabled him to author Person to Person: Friendship and Love in the Life and Theology of Hans Urs Von Balthasar, and, together with Msgr. Joseph Giandurco, he co-authored Partners in Life and Love: A Preparation Handbook for the Celebration of Catholic Marriage.
New York Governor George Pataki appointed Bonnici to a seven-year term on the board of trustees of the City University of New York in April 2002.
In 2002, Bishop Bonnici became the pastor of St. Philip Neri Parish in the Bronx, New York, until 2008, when he was assigned as pastor at St. Columba Parish in Chester, New York, serving there for the next 13 years. He also served as parochial administrator at St. Mary’s Parish in Washingtonville, New York, from 2020 to 2021. In 2021, he was named pastor of St. Augustine Parish and Sts. John and Paul Parish in Larchmont, New York.
On January 25, 2022, Pope Francis appointed Bonnici as an auxiliary bishop of New York and titular bishop of Arindela, and he was ordained to the episcopacy at St. Patrick’s Cathedral by Cardinal Timothy Dolan on March 1, 2022, with Auxiliary Bishops John O’Hara and Gerald Walsh serving as co-consecrators. Bishop Bonnici chose “To Jesus Through Mary” as his episcopal motto. After his episcopal consecration, Bishop Bonnici continued to serve as pastor of St. Augustine Parish and Sts. John and Paul Parish in Larchmont, while he also served as the episcopal vicar for Westchester and Rockland counties as an auxiliary bishop.
In addition to his responsibilities in the Archdiocese of New York, Bonnici serves as a member of the United States Conference of Catholic Bishops’ Committee on the Protection of Children and Young People and the Subcommittee on the Catechism. Since 2023, Bishop Bonnici has served on the Pontifical North American College’s Board of Governors representing Region II. Additionally, Bishop Bonnici serves as a member of the board of Aid to the Church in Need (ACN United States), which provides pastoral and humanitarian assistance to the persecuted Church around the world, and as a member of the board of The Christopher Missions Foundation, which primarily assists the Diocese of Miao, India, in establishing village churches, building parish schools, providing clean drinking water wells, ministry to at-risk women, and economic sustainability projects.
On January 7, 2026, Pope Leo XIV appointed Bishop Bonnici to succeed Bishop Salvatore R. Matano as the 10th bishop of Rochester. Bishop Bonnici will be installed as the bishop of Rochester on March 19, 2026, the Solemnity of St. Joseph.