Msgr. Seamus Brennan is the fifth child of James and Mary (Martin) Brennan and was born and raised on the family farm in County Laois, Ireland together with four sisters and eight brothers. Educated in the local National School and the Christian Brothers School in Athy County Kildare, he went on to study for the priesthood at Saint John's Seminary in Waterford Ireland for the Diocese of Trenton. Msgr. Brennan was Ordained on June 4, 1972 in Holy Trinity Cathedral, Waterford by Bishop Michael Russell. His first assignment was to Saint Barnabas Church in Bayville, NJ where he served as Parochial Vicar from 1972 to 1974. In 1974, he was transferred to Saints Philip and James Parish in Phillipsburg, NJ where he served until January 1982, when he was appointed pastor of Saint John the Evangelist Church in Lambertville, NJ. Subsequent assignments included Pastorate of Saint Matthews, Edison (1985-2002) and Immaculate Conception, Somerville (2002-2020). Msgr. Brennan then served as a temporary administrator of Nativity of the Lord, Monroe Township, NJ and senior priest at Saint Matthias, Somerset, NJ until his retirement in July, 2023 when he moved to Saint James, Basking Ridge as a retired priest in residence.

 Msgr. Brennan served the Diocese of Metuchen as the Director of the Office of Priest's Personnel from 1989-2001, and currently serves on the Presbyteral Council and the Board of Consultors. He celebrates weekend Masses at McCauley Hall in Watchung, Saint Rose of Lima in Oxford, Saint Patrick's in Belvedere, Transfiguration of the Lord in Highland Park, and other parishes as requested.

Msgr. Brennan's hobbies include reading, golf, cycling, walking and a little gardening.