According to the UK census of 2011, the parish had a population of 514.
The parish was part of the hundred of Frome and the Frome Rural District (1894-1974). Leigh upon Mendip was not an ancient parish, but a chapelry within the parish of Mells. It was also considered to be in Mells and Leigh Hundred.
1822 - Somersetshire delineated by Christopher & John Greenwood
A parish in the liberty of Mells and Leigh,and locally in the hundred of Kilmersdon, 5½ miles W. from Frome; containing 149 inhabited houses, and as many families, 148 of whom are employed in agriculture. The church is a Gothic structure, dedicated to St. Giles, and consists of a nave, chancel, two side aisles and porch, with an embattled tower containing six bells, and is a chapel to the adjoining parish of Mells. Population, 1801, 534 — 1811, 562 — 1821, 666.
1875 - Somersetshire edited by Edward Robert Kelly
Leigh-upon-Mendip is a parish and village, 120 miles from London, 3 north-east from Cranmore railway station, and 6 north-east from Shepton Mallet, in the Eastern division of the county, hundred of Mells and Leigh, union, county court district and rural deanery of Frome, Wells archdeaconry, and diocese of Bath and Wells. The parish is considered very healthy; it is well supplied with excellent water, and is 8S4 feet above the level of the sea. The church of St. Giles is an ancient stone building, in the Perpendicular style; has a chancel, nave, aisles, elaborately decorated tower with pinnacles, containing 6 bells, and clock, porch and organ. The register dates from the year 1566. The living is a chapelry, yearly value £200, annexed to the vicarage of Vobster, in the gilt of the rector of Mells, and held by the Rev. George Augustus Mahon, M.A., of Hertford College, Oxford. There is a school for boys and girls. The Wesleyans and Primitive Methodists have chapels here. J. F. Fortescue Horner, esq., of Mells, is lord of the manor, and owns nearly the whole of the parish. The soil is generally light, resting on the limestone, and, in portions of the parish, on the clay subsoil. The land is chiefly in pasture, producing a sweet herbage for dairy purposes. The acreage is £1,425; rateable value, £3,009; the population in 1871 was 512.
1929 - Somerset by George Woosung Wade & Joseph Henry Wade
Leigh on Mendip (pronounced Lye), a bleakly situated village on the E. Mendips, 6 m. W.S.W. from Frome. It possesses a small Perp. church with a mean chancel, but set off by the compensating attraction of a remarkably noble W. tower, which well merits attention. It is of the reduplicated triple window type (cp. Mells) with a finely pierced parapet and profusely ornamented with pinnacles, but out of all proportion to the church. The latter contains (1) a pillar stoup in the porch; (2) a Norm, font; (3) some old oak benches; (4) fine granite altar slab, found buried for safety's sake; (5) two small corbels in the chancel, presumably for supporting a Lenten veil (cp. Orchardleigh); (6) piscinas in chancel and S. aisle.