St Peter's is situated within a curvilinear churchyard, bounded by roads on all sides. A Roman military settlement, Cefn Gaer (NPRN 300159) is situated some 580m to its south-east, with a motte (NPRN 302965) some 300m to its south-west. As Pennal was the commotal centre for Ystrumanner it was a place of some significance in the medieval period. The first documentary reference to the church was 1254. The road to the south was widened in 1991, at which time 91 memorials were recorded and removed (being subsequently laid flat against the churchyard walls). Fragments of Roman tile were also found. At this time the south-west corner of the churchyard was lowered. There are entrances to the churchyard, one in the west wall, and the other a lych gate in the south-east. Roman brick has been identified in the in the churchyard wall to the south of the west gate.

The present church is a Grade 2 listed building. It was rebuilt in 1769, re-using much fabric from its predecessor. The church building consists of a continuous nave and chancel, a south porch, north vestry and low square tower. Roman brick is built into the eastern end of the north wall of the church. The roof retains some late sixteenth or early seventeenth century timbers. In 1890 the vestry was added on the west end of the north wall. The internal floor area was lowered by two feet and six inches around 1901. Wooden arches at the west end of the building may indicate the position of a former gallery. The three oak plaques on the north wall are imported from elsewhere, as are two panels at its west end.

Sources include:
Beverley Smith, J, Beverley Smith, Ll, 2001, History of Merioneth II, 366-7
Gwynedd Archaeological Trust, 2000, Historic churches of Gwynedd: gazetteer, 391

N Vousden, RCAHMW, April 2012