The nave has 5-bay arcades with alternating circular and octagonal piers, with moulded capitals supporting pointed arches with double chamfers. Nine-bay roof with arched braces, arched wind braces, low-set tie beams and moulded wall plates with dentils. Benches to either side of a central aisle with moulded arm rests. Pointed chamfered doorway at E end of N aisle leading to vestry. Four-centred tower arch with narrow mouldings. Half-glazed wood panelled screen across tower arch with stained glass and a dentilled decorated cornice. It is a memorial to the Rev Canon John Powell Jones, vicar of the parish 1865-83. There is said to be a baptistery under the tower floor. Small chamfered pointed arched doorway in N wall of tower chamber leading to stair turret, and C20 stairs on S side. Tall pointed chancel arch, double chamfered, on triple shafts with foliate capitals and wide polygonal bases. Three-bay chancel roof, the E bay with sound-boarding, the other 2 bays with arched braces and a central ridge piece. Wood panelled reredos with cusped blind arches with ogee heads.
C15 octagonal stone font on square base with broach stops and a chip-carved circular design to each face (similar to the fonts at Pyle and Llanharry). Small organ to L front of nave, and polygonal wooden pulpit to R by George Pace, 1967. In the S aisle is an altar, behind which is an Early Christian grave slab incised with a circular cross flanked by smaller crosses.
Stained glass to E window depicting the Crucifixion and Mary and John, dated 1873. By Morris & Co. and designed by Burne-Jones. It was commissioned by John Prichard in memory of his relatives who had lived in the parish. The 2 lancets to the S side of the chancel are contemporary and by Clayton & Bell. They are in memory of Rev Evan Morgan and his wife Letitia (d.1864 and 1868), and depict the Charge to Peter and Noli me Tangere. The L window of the S aisle shows Saints Peter, Paul and John and was presented by Evan Evans in memory of his brothers. It is also of 1873 and by G H Cook. The stained glass window to the R is a First World War memorial depicting soldiers. R window to N aisle in memory of David Henry Simon, vicar of the parish, 1923-39. The remaining windows contain pink and yellow glass.
An effigy of a C13 warrior wearing a simple tunic and head-dress is set into the wall at the E end of the N aisle. It depicts Cadwgan Fawr of Miskin, one of the Welsh opponents of Gilbert de Clare, Lord of Glamorgan, 1217-30. It was moved to this position in 1873. There are many stone and marble wall monuments in the church. Above the effigy is a marble tablet with fluted pilasters and cornice, dated 1742, but hard to read. At the W end of the N aisle is a black slate tablet with round arched head and decorated with scrolls and vases, to Ann, daughter of Morgan David (d.1740), aged 36. Memorials to the Barrett family of Miskin including S aisle, to R of doorway, a stone tablet with arched head, listing members of the family who died C17-18. In the S aisle, a memorial in the form of a scroll to the Lewis family. Marble tablet with shield to L, to Richard Evans (d.1866) of Watling Street, London. To the R of the chancel arch is a tablet bearing a draped urn to Anne Thomas of Ynys y Plwm (d.1845), signed Porter. Tall stone tablet in chancel, raised from ground, to Mary, wife of Evan Prichard (d.1740) and other members of the family. On the S wall of the chancel is a large marble tablet with arched head and scrollwork to Dr Richard Thomas (d.1733). To the R is an plaque with head boss, to Mary, wife of Henry Nichols (d.1735).