File:Glentham, St Peter's church (27282631815).jpg

The nave and aisles are C15 and were much repaired in 1855 and the south aisle in 1936. The windows are Perpendicular in the north and south aisles with two earlier from the C13.

The vestry was a mortuary chapel of the Tourneys and also contains a C14 brass.

It appears the east end of the church was shortened, possibly in the C17, and an incomplete arch can be seen in the north aisle.

The organ on the gallery at the west end is by Forster and Andrews of Hull. This cost £80 in 1836 and was originally at the east end of the south aisle.

The tower has four bells cast in 1687 but due to the age and decay of the frame and fitting they can no longer be rung properly.

The font has a late C12 base with a circular stiff leaf capital. The top was added in 1916. The medieval door has its original Sanctuary ring.

Under the organ loft lies an old stone effigy to one of the Tourney ladies, known locally as Molly Grimes. The ancient ritual of washing holy images on Good Friday was perpetuated in Glentham until 1832, using this effigy. A rent charge of seven shillings a year had been left on some land to pay seven virgins to perform this task, the water being carried from the Neu Well near Caenby Corner. When the land was sold about 1832 with no reservation on this rent charge, the custom fell into disuse. Some reference books describe the name "Molly Grimes" as being a mispronounciation of an old dialect word "Malgraen". A more recent interpretation has been suggested that Grimes comes from the old Norse "Grimr" meaning "mask of evil", or covering of darkness or dirt. In more recent times, the custom has been revived by the holding of the Molly Grimes run, with contestants racing with water from the well to the church.

On the porch is a stone effigy of Mary holding Christ – a rare survival of the Reformation – and the only one of its type in Lincolnshire. The Coat Of Arms containing 3 bulls with a chevron band belongs to the Tourney (or Tournay) family.