The Consistory Courts of the Chancellor of the Diocese of St Davids took place at the church and Bishop Robert Ferrar was tried here in 1555.

[1]One of the best-known people to be buried at St Peter's is the 18th-century satirist, Sir Richard Steele, who married a local woman, Mary Scurlock, and died in Carmarthen in 1729.

The main body of the church consists of a long nave and chancel, separated from the south aisle by five arched bays.

The decorative floor tiling in the chancel and aisles dates from 1866/76 and is by Maw & Co.[2] There are a large number of important tombs and memorials inside the church.

[1] The tomb of Rhys ap Thomas, reputed to have made the fatal blow to King Richard III, is located inside the church.

[8][9] The northwest entrance to the churchyard (in front of the church tower) is via a red sandstone neo-Gothic lychgate and a set of iron gates.

[10] In 2014 the vicar, Reverend Leigh Richardson, announced that the church had very little financial reserves to draw on and, with running costs of £50,000 per year it was under threat of closure.

[8] In its Historia Regum Britanniae, Geoffrey of Monmouth writes that Merlin's mother used to live with nuns in the church of St Peter in Carmarthen.