Monsignor William J. Fadrowski is a native of Bayonne, New Jersey, where he attended Saint Joseph School and Marist High School. After graduation from Marist in 1962, he entered the Congregation of the Marist Brothers of the Schools and remained a member of that religious community for 25 years until his ordination to the priesthood.

Monsignor Fadrowski was a teacher and guidance counselor at Union Catholic High School, Scotch Plains, New Jersey, from 1966 to 1972. In 1972, he joined the faculty of his alma mater, Marist High School, as a guidance counselor and chairman of the Religious Education Department. During that time, he was also involved in youth ministry and retreat work. In 1980, he became Assistant Superintendent of Schools for the Archdiocese of Newark, with responsibility for religious education and youth ministry in the Catholic high schools of the archdiocese.

He was ordained to the priesthood in November 1987 for service in the Archdiocese of Newark. In January 1988, he was assigned as Parochial Vicar at Queen of Peace Church in North Arlington and was appointed Pastor in 1999.

In March 1991, Monsignor Fadrowski became the Director of the Archdiocesan Catechetical Office, with responsibility for Religious Education in the parishes and schools of the archdiocese. He has served on numerous archdiocesan committees, including the Papal Visit Task Force, which welcomed Pope Saint John Paul II to the Archdiocese of Newark in 1995, and the Archdiocesan Synod Implementation Committee. On a national level, he served as a member of the Board of Directors of the National Catholic Educational Association. In January 1996, Monsignor Fadrowski was appointed Executive Director of the Office of Clergy Personnel and Director of Priest Personnel of the Archdiocese of Newark. He continued in this position until June 2003.

In January 2000, Monsignor Fadrowski was appointed a Chaplain of Honor to His Holiness, Pope John Paul II with the title Reverend Monsignor. In May 2008, Monsignor Fadrowski was honored by the Knights of Columbus as Chaplain of the Year for the State of New Jersey. In November of the same year, he was invested as a Deputy Chaplain of the Order of Malta at the Cathedral of Saint Patrick in New York City. In 2009, Monsignor Fadrowski was appointed a Prelate of Honor to His Holiness, Pope Benedict XVI. In November 2011, he was elevated to Magistral Chaplain in the Order of Malta in the Cathedral of Saint Patrick in New York City. In February 2012, Monsignor Fadrowski was appointed Dean of the South Bergen Deanery of the Archdiocese of Newark. In 2013, Monsignor Fadrowski became a member of the Board of Directors of From Houses to Homes Guatemala, an organization that builds houses for poor families in rural villages in Guatemala. The group also runs a medical clinic and two elementary schools.

In May 2016, Monsignor Fadrowski retired as Pastor of Queen of Peace Parish but remains active in priestly ministry.

Monsignor Fadrowski holds a Bachelor of Arts degree in French from Marist College, Poughkeepsie, New York; a Master of Arts in Education and a Master of Divinity in Pastoral Ministry, both from Seton Hall University.