St Michael's Church is situated within a curvilianear churchyard, on a right-angled cornerof the B4459 road. The church was a parish church during the medieval period, belonging to the Deanery of Stradtowy. In 1360 it was granted to the priory of St John, Carmarthen, by Edward of Woodstock, Prince of Wales (the Black Prince). At the dissolution the advowson fell to the crown, but subsequently found its way into private patronage. In 1833 the living was a discharged vicarage in the alternate patronage of William Lweis and J.R.L. Lloyd Esq. During the post conquest period Capel Mair (now St Mary's Church), Pencader (NPRN 418670) was a chapel of ease belonging to St Michael's Church. It has been suggested that Llanfihangel-ar-arth was originally known as Llanfihangel Ioreth. In 1535 the name was given as 'Llanfihangel Orarth'. There is a Latin inscribed stone in the south aisle of the church (formerly in the churchyard). Its inscription reads 'HIC IACIT VLCAGNUS FI[LI]US SENOMAGLI'. A cross-incised stone, possibly a post-conquest alter table, currently stands upright in the churchyard, although it was noted to be leaning against the church's exterior east wall.

The church is a Grade II listed building, constructed of predominantly Silurian mudstone rubble. It consists of two-bayed nave, two-bayed chancel, four-bayed south aisle, south porch, boilerhouse (north of chancel west bay) and (single) bellcote. The nave and chancel are thought to date to the thirteenth century. The south aisle east bays are thought to date to around 1500, with its west bays possibly dating to around the early sixteenth century. The octagonal limestone font is though to be fourteenth-fifteenth century in date. In 1552 there were two bells. The outline of a double bellcote is visible in the nave west wall. The church was restored in the mid-nineteenth century, when the south porch was added. The south door may also have been inserted at this time. The boilerhouse, constructed of breeze blocks, was added in the late twentieth century.

Sources include:
Cambria Archaeology, 2000, Carmarthenshire Churches, gazetteer, 48

N Vousden, RCAHMW, 30 April 2013