A vicar general is appointed in a diocese to assist the bishop in the administration and pastoral care of the diocese, representing and acting in the place of the bishop in his absence. A vicar general has executive but not legislative or judicial authority. The large scope and executive nature of the office requires that the vicar general be of sound doctrine, of integrity, of prudence, and well versed in both canon law and theology. 

A graduate of Biddeford High School, Fr. Greenleaf went on to earn bachelor’s degrees in accounting from the University of Southern Maine and in sacred theology from the Catholic University of America in Washington, D.C.; he later completed a license in sacred theology in spirituality from the University of St. Thomas Aquinas in Rome.  Fr. Greenleaf was ordained to the priesthood by Bishop Joseph J. Gerry on May 13, 1995, at St. Joseph Church in Biddeford. His first assignment was as parochial vicar at St. John Parish in Bangor. He was named director of vocations for the Diocese of Portland in 1997. Two years later, in addition to his duties as director of vocations, Fr. Greenleaf was appointed chaplain and faculty member of St. Dominic Regional High School in Auburn. In 2002, he was named administrator of St. Joseph Parish in Lewiston. In 2004, Fr. Greenleaf was appointed pastor of Holy Cross Parish in Lewiston. From 2009 to 2012, Fr. Greenleaf was part of the formation faculty at Theological College in Washington, D.C. In August of 2012, he was named pastor of the Parish of the Holy Eucharist, and in July of 2014, he also became director of seminarians for the Diocese of Portland, positions he still holds. In addition, Fr. Greenleaf has assisted with diocesan youth ministry and Catholic scouting.