St Thomas' Church was built in the Victorian early-Gothic style to a design by architect Ewan Christian, with its foundation stone laid on 9 July 1846 and the church opened on 1 August 1849. Its most celebrated feature is a vast scheme of decorative murals, covering roughly 520 square metres of the chancel and nave, painted between 1896 and 1910 by the Douglas-based artist John Miller Nicholson at the instigation of the then vicar, Canon Savage. The church also holds a First World War memorial designed by Archibald Knox, unveiled on 11 November 1923 in Scotch green slate with gold lettering and listing 104 parishioners who died in the war; it was originally mounted on the exterior west wall and later moved into the Memorial Chapel in the north aisle. Other features include stained glass windows, a three-manual organ, and a bell and clock tower.