The Church was built around 1150 AD in the late Romanesque style of locally-won limestone rubble, ironstone and flints, with finer quality dressed limestone from Oxfordshire. It is a typical Norman three-cell construction of Nave, Chancel and Sanctuary with a massive central Tower above the Chancel, and survives as one of only three Norman churches of the same style and date, without having serious alteration to their original footprint plan.

Stewkley represents ten different late Romanesque stone carving styles, but chevron patterns are dominant, on the Chancel and Sanctuary arches, the window and door surrounds, and the internal and external string-courses.

St Michael´s was conservatively restored in 1862 by the eminent Victorian architect, G E Street. The roofs were restored to their original Norman pitches, the small oculus window added to the West gable, and stone buttresses at the Sanctuary corners. Street himself designed the neo-Norman pulpit and the exotic Sanctuary reredos, added new pews, and employed Messrs Clayton and Bell to re-decorate the Sanctuary vaulted ceiling and to install a new stained glass East window.

In 2000-06 and again in 2012, a modern programme of conservation work took place to conserve and replace eroded ashlar and rubble limestone, and to repoint the external walls throughout the church with lime mortar to permit the ancient fabric to breathe.