A native of Paterson, Father Mancini was graduated from Passaic County Technical and Vocational High School, Wayne. Before studying for the priesthood, he was an assistant industrial electrical foreman with Standard Environmental Systems, Totowa. He received a bachelor’s degree from Seton Hall University in South Orange and completed priesthood studies at St. Mary Seminary and University, Baltimore. He was ordained on Nov. 28, 1992 and his first assignment was a parochial vicar at St. Therese Parish, Succasunna. He was later named pastor of St. Simon Parish in Green Pond and served as Dean for the Northern Morris Deanery. In 2011, he returned to St. Therese as pastor there before his appointment as pastor of St. James. On May 1, 2021, Bishop Kevin Sweeney had appointed Father Marc as diocesan Judicial Vicar for the Tribunal Office.