Report on an archaeological watching brief, conducted during groundworks for new drainage at St Denys' Church, Sleaford. The monitoring recorded medieval activity, in the form of foundations of the western part of the south aisle wall, and two limestone slabs, thought to possibly have served as gravestones. Later activity was also recorded, in the form of a number of graveyard soils and charnel deposits, a brick lined grave and a portion of an articulated human skeleton. Finds recovered included a range of medieval and later pottery, tile, jettons, window glass and coffin fittings.