Built into the north wall of the church nave—likely by 17th- or early 18th-century restorers—is an early example from the York school of craftsmen. Its legs were broken off and the body rotated horizontally to fit the current position and accommodate the pulpit. When the antiquary Roger Dodsworth visited in 1627, the effigy lay on the north side of the chancel, probably in a recess. Dating to around 1270, it is considered one of the oldest surviving medieval effigies in Yorkshire. The shield bears the Bulmer arms—gules, billety, a lion rampant or—and likely commemorates Sir John de Bulmer III (d. 1268).

The early lineage of the Bulmers of Bulmer, and later Wilton-in-Cleveland, is unclear, and their link to the well-known Ansketil de Bulmer is uncertain. Sir John III seems to have been the great-great-grandson of Stephen de Bulmer, lord of Bulmer, who may have been a younger brother of Alan de Wilton I and a son of Ralph de Farlington. Sir John III succeeded his father, also Sir John, and his wife Alice. In 1235–6, the elder Sir John inherited Wilton-in-Cleveland from a relative, Thomas de Wilton. He mainly lived at Bulmer, received free warren rights in 1251, and died in 1268. His widow Katherine (née Salvin) gave up her dower claim in favour of their son, Sir John IV (d. 1299), a distinguished soldier buried at Guisborough Priory.

The effigy is heavily covered in whitewash. The knight wears a rounded skull-cap under a mail coif, secured with leather thongs and a headband. The mittens, part of the hauberk sleeves, have thumb-pieces but no finger separation. His hands are raised in prayer. A guige runs over the right shoulder to support a heater-shaped shield with the Bulmer arms, carved in a rough style. The sleeveless surcoat is belted at the waist with a narrow strap, its end hanging down the left side. The sword, once with straight quillons, and its belt are both badly damaged.