Capel Mair is thought to have been a medieval chapel of ease. Historic Ordnance Survey mapping depicts the building on the site as Capel-Mair school. In 1912 it was noted that the building was a modern one, and modern Ordnance Survey mapping depicts it as a hall. A well, Ffynnon Fair, is located some 560m to the north. A motte (NPRN 401200) is located 190m to the south-south-west. A standing stone, known as Garreg Lwyd (NPRN 303799), is situated some 420m to the south-west of the chapel site. In 1828 a late fifth-sixth century inscribed stone was first noted in the churchyard. it remained in situ for a few years, before being moved to the farm yard of adjacent Dancapel, where it was used to block an opening between two out-houses to prevent the passage of pigs. in order to prevent people from moving the stone to read the inscription, the farmer is said to have smashed the stone into pieces and used it to repair his barn wall. He is then said to have placed a similar stone in the cemetary and to have informed people that the inscription had worn away. Some years after the farmer's death, labourers came accross some small fragments of the stone while repairing the barn. These were preserved in the vestry of the modern Capel Mair, and were inspected by RCAHMW staff in 1912. By 1931 only one fragment remained. Its measurements are given as 17in x 12in x 3in thick, and its inscription read 'DE
FII'.
Fortunately, a former Vicar made a sketch plan of the stone before it was destroyed. The inscription has been translated as either 'Decabar balom, son of Brocagnus' or 'Deccaibur the Poor lies here'. The stone is said to have originally been some 6in thick, with an estimated length of 10ft and width of 2ft.

The building is thought to have been restored in the early nineteenth century. In 1850 the building was described as being whitewashed, and consisting of nave, chancel and a south chapel seperated from the chancel and east part of the nave by two rude pointed arches. It was also noted to have a square-headed east window, a niche over the west door, two open arches for bells in the west gable. Sash windows were noted in the north wall. The building was used as a school from 1849. In 1898 the present St Mary's Church was erected to the immediate south. The former chapel was then used exclusively as a school, with its former cemetary becoming the school playground. The bell belonging to Capel Mair is said to have hung in a tree for many years, before being removed to Llysnewydd, a house in the parish. In 1931 Capel Mair's font was noted to lie inverted in a gutter in the field below the chapel. It was described as appearing to have been formed by splitting a boulder in half and hollowing out the flat side of one of the halves.

Modern Ordnance Survey mapping depicts the building as a hall.

Sources include:
Jones, F.,1931, 'Llangeler Parish: Notes on Some of its Ancient Monuments' in Transactions of the Carmarthenshire Antiquary Society, Vol XXIII
Ordnance Survey, 2012, 1:10,000

N Vousden, RCAHMW, 18 September 2012