The church dates from circa 1300 onwards. It was restored in 1867 and 1887. It is one of the finest 14th century churches in England. Built between 1305 and 1333, it replaced an earlier church which was recorded in the Domesday book. The church was probably begun by Lora de Gant, Lady of the Manor of Heckington. Its greatest glories are due to the generosity of two men linked with King Edward II, Lord Henry de Beaumont and master Richard de Potesgrave. Beaumont's coat of arms once appeared in many of the stained-glass windows. Richard de Potesgrave (circa 1275 to 1349) was rector of Heckington in 1309 and was the Kings' chaplain. In 1321 he was given custody of Leeds Castle in Kent.

The church consists of a west tower with spire, clerestoried nave, north and south aisles, transepts, chancel, south porch and north Chapel The three stage tower and spire is 185 feet high with three tiers of lucarnes. There are multiple gargoyles on gabled niches as well as on crocketted pinnacles.

The south porch dates from the decorated period although suffered from vandalism to statues in niches. Over the entrance is a statue of Christ in Glory. Inside, there are four bay north and south nave arcades with octagonal piers. There was originally a Rood screen separating the nave and the chancel. The north aisle is probably the oldest part of the church and the north transept was formerly used as a Chantry Chapel, the piscina is still in position. The south transept, has its own sedilia, and in the south-west corner there is a burial slab with an engraved bust, possibly Potesgrave's father from the 14th century. The south transept was probably the "Chantry of Saint Nicolas" where rector Potesgrave's parents were prayed for.

The chancel was built by Potesgrave whose tomb is recessed into the north wall with a damaged effigy. He died in 1349 aged about 75, possibly of the Black Death. When the tomb was opened in 1800 his communion chalice was found inside. The east window is 34 foot high and 16 feet wide with seven lights. On the north wall of the chancel is an Easter Sepulchre, complete with sleeping soldiers beneath crocketted gables. To either side are figures, and above is the risen Christ attended by censing Angels. The Sepulchre was also used as a permanent sacrament shrine, where consecrated bread and wine were kept.