[2][3] Historic England describe St Mary's as "large and lavish" with a "high quality finish".

[4] The church is largely built with Purbeck Marble, with some facings and window surrounds in Bath stone.

[5] St Mary's Church was built in 1910–12 to replace an earlier one of timber and corrugated iron, known as the Tin Tabernacle, which had been erected at the Top O'Town in 1896–97 to serve West Fordington, during a time when the population of Dorchester and its suburbs was increasing significantly.

[2] In 1907, disagreements over the church's location emerged between the parishioners and vicar of West Fordington and the Bishop of Salisbury, John Wordsworth: Bishop Wordsworth opposed building at the site of the Tin Tabernacle, believing that the new church would be better positioned further south.

On 21 April 1910, Anthony Ashley-Cooper, 9th Earl of Shaftesbury, laid the foundation stone of St Mary's; the church was consecrated two years later, on 11 July 1912.