The church dates from the 13th century onwards. Low Marnham is mentioned in the Domesday Book as being under the Lordship of Roger de Busli.

There is a tower, nave with north and south aisles and clerestory, south porch, north chapel, and chancel. The two-stage tower has an embattled parapet, crocketted pinnacles and gargoyles. The exterior of the nave has 15th century windows with gargoyles, and the 15th century clerestory also has three-light windows and gargoyles.

The south door has an elaborate ogee arch with no capitals. The nave has 13th century three-bay arcades, the south arcade has octagonal cores surrounded by detached shafts with capitals decorated with leaves and crocketts. These may have been the work of the same Masons as at Lincoln Cathedral. The north arcade has round columns, and also dates from the 13th century. The chancel arch is 13th century with the Royal Arms displayed above, dating from the reign of George II. There is a two-bay 13th century arcade to the north chapel. The south wall of the south aisle has a piscina and aumbry.

There are several 17th and 18th century wall monuments in the nave and aisles. One window has 15th century stained glass depicting St James. The font dates from the 18th century, and is plain and octagonal with a wooden cover.

The church was placed in the care of the Churches Conservation Trust in 1986.