The village straddles the River Gwili between Bronwydd and Llanllawddog, at the confluence of two small tributaries, Nant-cwm-cerwyn and Nant Aeron.

The name Llanpumsaint translates as "Parish of the Five Saints" ("Llan" means church or enclosed area of land).

The five saints were brothers named Gwyn, Gwynno, Gwynoro, Ceitho and Celynin who came from the nearby hamlet of Cynwyl Gaeo.

One of the brothers, Ceitho, is the patron saint of Llangeitho in Ceredigion where he founded an abbey and lived as a hermit there within.

[7] At Allt Pant Glas, to the south of Llanpumsaint village, there are earthworks indicating the site of a possible medieval timber castle of the motte and bailey or ringwork form.

The railway served the village for over 100 years until the line finally closed (having ceased carrying passengers in February 1965 and the station).

Freight trains continued to pass through the village on their way between Felin Fach and Carmarthen until 1973 when the line was finally closed and lifted.

In neighbouring Bronwydd, a 1 mile long section of the line was reopened in 1978 for tourists and named the Gwili Railway.

[11] The east window of the nave was designed by Mildred "Elsi" Eldridge, the wife of renowned Welsh poet R. S.