The history of the Catholic Church in Saco begins on the Feast of the Assumption, August 15, 1827, when Bishop Fenwick of Boston celebrated Mass at the home of Dr.Harvey Green (now 374 Main Street). Saco Catholics celebrated Mass and received the Sacraments in Biddeford from that time until November 2, 1916, when Most Holy Trinity Parish was formed, with the Rev. Timothy J.Mahoney as pastor.

The present rectory, the historic KingWoodman House, was purchased on November 2, 1914. It had been built in 1807 by Cyrus King and later owned by Horace Woodman. The building that served as the first church was built about 1767 and served as both a home and a theater before Father Mahoney purchased it two days after Christmas in 1918. The first mass was celebrated by Father Mahoney in the partially renovated building on June 9, 1938. It was dedicated on July 17 the same year. Father Mahoney served all Saco Catholics until many of his French-speaking parishioners founded Notre Dame de Lourdes in 1929.

The much-loved and admired Reverend Francis McFarland succeeded Father Mahoney. Through his unfailing affability and dedication to his church and its parishioners, Father McPartland did much to raise the esteem and good will of his fellow citizens towards his parish. Upon Father McFarland's death in 1950, Reverend Mauico Boland was appointed as new pastor. He celebrated his Golden Jubilee of Ordination in 1966, the same year Most Holy Trinity Parish celebrated its Golden Anniversary. Father Boland encouraged the formation of the Christine Doctrine. He also acquired a house on High St. as a convent for the Franciscan Sisters of Atonement, who came to the Parish in 1959.

Reverend James Daly, who was instrumental in implementing many of the changes brought about by Vatican II, as well as building the Parish Hall, succeeded Father Boland in 1967. Father Daly retired in 1973, to be followed by Reverend Norman Comier, who served as interim pastor until the appointment of Father Robert Brennan, CSC. Father Brennan's arrival marked the assumption of the pastoral duties of Most Holy Trinity parish by the Eastern Province of the Holy Cross Fathers. Together with Father Jack Walsh, his associate, they continued to implement the changes brought about by Vatican II, as well as begin a major restoration of the church.

In 1979, Father Brennan was reassigned and replaced by Reverend Lawrence Jerge, CSC, who completed and introduced the Rite of Christian Initiation of Adults in accordance with Vatican II decisions. In 1982, Reverend Leo Polselli, CSC, was appointed pastor when Father Jerge was reassigned. Father Polselli was especially active in furthering Church Christian to a growing and increasingly active parish. Father Leo served as pastor of the Most Holy Trinity until September, 1986, when he was appointed Assistant General in Rome for the Congregation of Holy Cross Fathers and Brothers.

When the position of Pastor became vacant in 1986, Reverend James David, CSC, (then assistant pastor) became interim pastor. In April of 1987, Father Jim became the fourth Holy Cross Father to be named pastor of Most Holy Trinity Parish. It was during the pastorate of Father Jim that the Parish Community would take on the huge task of planning and bringing into reality a new church building. The building that had been home to the Parish since 1916 had become inadequate. Many hours of planning and many meetings would take place as the Parish Community sought to bring into existence a building that would express the sense of sacredness and beauty which should characterize a house of worship. Research and study about the liturgical ideals as expressed by Vatican II were carefully reviewed. It was on October 10th, 1993 that
Most Rev. Joseph J. Gerry, OSB, the Bishop of Portland, would bless this new edifice. The blessings came at the beginning of the Pastorate of Father George B. Mulligan, CSC, who was
chosen to succeed Father Jim, whose term of office had come to a close.

A meals program for the needy would be instituted. The Head Start Program was given space in the classroom wing of the Parish Hall, and a support group for the mentally ill would be founded and developed under the leadership of Michael Arenstam, a member of the parish community. Reverend James Doherty, CSC, was named the successor to Father George. Father Jim brought his own special gifts and insights to the Parish Community, and he continued his ministry here as the sixth Holy Cross Father to be the pastor of Most Holy Trinity Parish. Fr. Jim served Most Holy Trinity Parish as pastor until August, 2005.