St Mungo's is constructed in red sandstone rubble with a sandstone slate roof. It has coped gables on which are cross finials. The plan consists of a two-bay nave with a north aisle, a south porch and a north vestry, and a two-bay chancel with side chapels and a lean-to hearse house. On the west gable is a twin bellcote and on the east gable is another bellcote for the angelus bell. In the porch is a re-set Norman doorway with zigzag carving. On the east wall of the nave on each side of the chancel arch are stretches of a Norman frieze decorated with saltaire crosses. The church originally had transepts, but due to extensions of the church, they now lie east of the chancel arch, the north transept having been absorbed in the aisle. The south chapel was originally a chantry, then walled off from the chancel, has been made into a memorial to the victims of the First World War, and is known as St George's chapel. The south chapel is the Crookdake Chapel and contains a graveslab to Adam Crookdake who died in 1304.
