He discerned a vocation to the priesthood and was ordained a priest of the Archdiocese of Washington in 1990.
In 2006, Fisher was appointed vicar for clergy and secretary for ministerial leadership, with responsibility for vocations, formation and care of the clergy for the archdiocese.
Pope Francis named him auxiliary bishop of Washington in June 2018.
Over nearly 30 years of priesthood, Fisher served in several parishes and in leadership of different archdiocesan ministries, including on education, social justice, parish life, and youth.
He has also served on the archdiocese's administrative board, clergy personnel board, priest council, and priest retirement board, and, according to the press release, his ministry "has involved the continuing education of priests, particularly in aiding new pastors in their roles and the planning and implementation of ongoing clergy training via convocations and retreats."
Cardinal Wilton Gregory of Washington described Fisher as "an exceptionally compassionate and skilled servant of the Church."
"His distinguished history as pastor, Vicar for Priests, and member of our Pastoral Administration have prepared him well for his new responsibilities in that diocese. While we will miss his deft pastoral talents, they will be warmly welcomed by the faithful, religious, and clergy of the Diocese of Buffalo," Gregory said.