The church is in the ecclesiastical parish and Group of Ancaster and Wilsford, in the Deanery of Loveden, and the Diocese of Lincoln.

In 1873, the north aisle was extended and the chancel rebuilt by J. H. Hakewill, at a cost of £450, in a style that matched the Early English original.

[4][5] In the 19th and earlier 20th century, Welby was part of the rural deanery of Grantham North, and archdeaconry and Diocese of Lincoln.

The diary records reorientation of the seating, the 1872 addition of a stove in the body of the church, and in 1927, the partial laying of a concrete floor under the nave and chancel.

Finds included remains of a previous lime mortar floor, stained glass and window lead fragments, pottery of the 15th to 19th centuries, some graves, and shroud pins.

It is built in ashlar-dressed limestone rubble, originates from the 13th century, and is Early English and Perpendicular in style.

It consists of a chancel, nave, north aisle, a west-facing tower with spire, a vestry, and a south porch.

The Perpendicular "tall" south porch is surmounted by crocketed pinnacles on its gable canopy corners, which Pevsner describes as "oversized".

[7] Within the porch is a 14th-century stone tomb cover with relief depictions of a woman's head and shoulders within a quatrefoil recess, and a shrouded baby.