The first church founded in Beaminster was a Saxon Minster (church). Its exact location is not known, but is believed to have been on the same site as the present church buildings. This location was traditionally thought to have been a prehistoric sacred mound. The first Minster was probably founded by St. Aldhelm. The earliest known record was found in a charter of King Ethelred, dated 681. The Minster was originally in the diocese of Sherborne buy a charter of St. Osmund. In 1091, it was transferred to the Diocese of Salisbury. The original church was replaced by a Norman Minster sometime in the 12th century. It was staffed by the Benedictine Monks from the Gloucester Abbey, nearby. Minsters not only served large areas as a religious center, but also were the health and social services of their day. The Norman Minster was cruciform in shape with a central tower, nave, transepts, but no side aisles.
Building of the present church was started in 1440, using the foundations of the old Norman Minster. Construction was completed in 1480, leaving the original Norman tower in place. In the 1500's, the Norman tower was removed and replaced with the present bell tower, in the perpendicular style. This was one of the first successful attempts to abut a perpendicular tower against the body of an existing church. Today, little remains of the old Norman church except for the foundations and a few walls. There are three artifacts that remain from the original church: a late 12th century baptismal font, an early 13th century parish chest, and an early English piscine in the south aisle. Unfortunately, the central polypoid support of the baptismal font is a modern restoration. The piscine originally belonged to the altar of St. Mary and St. Juthware. The later was a local martyr. There was considerable pilgrimage to this altar in mediaeval times. At the east side of the south aisle can still be seen an original squint and rood loft stairs. In early times, there was no seating for the congregation except for a few benches around the walls for the infirm (sick) and elderly. The stone floor was covered with rushes and changed each September with great ceremony. In 1619, the present pulpit was made by two local men and the church began to be filled with box pews. Between 1634 and 1637, galleries were erected in the north and south aisles and later across the west end and now seats 986 people. The galleries and box pews were removed in 1861. Wood from the galleries was used to construct new bench pews. In 1984, the wooden pews became infested with Death-Watch Beetles and had to be replaced with chairs. During the 18th century, the Strode family took over the south aisle and installed box pews, burial vault, and two monumental sculptures by a well known sculptor, Scheemakers.
The Mort House apparently had been a separate building at one time, but has now become part of the main church structure. The Mort House originally had two stories and housed a school for 20 poor boys on the second story. The school moved out of the Mort House in 1734.