Broad nave with painted plastered walls and panelled C15 barrel roof of 10 by 16 panels, the wall-plate panels of half size, and the timbers moulded. Plaster restored to the panels in 1987. Plastered pointed vault to the tower with small pointed red stone door to winding tower stair. High on nave W wall is door into tower. Broad rough stone segmental pointed chancel arch, double chamfered arch, single chamfer to piers. The nave has lower rood-stair door on N side, purple stone, segmental-pointed, chamfered with diagonal stops. C19 plank door with wrought iron hinges. Upper rood-loft opening in angle to E wall, segmental pointed with stone left jamb. Windows in plastered cambered-headed reveals. Chancel is slightly out of alignment. Similar barrel roof of 10 by 12 panels, the panels smaller than those of nave. One step to sanctuary, one to altar. Ornate E wall encaustic tiling, also on sloping sill of E window, with evangelist symbols, 1888 to D. Jeffreys Powell. Tomb recess on S wall with low Tudor-arched head.
Fittings: C19 octagonal font, 1869, on octagonal shaft, the bowl lettered in large Gothic capitals 'Christian'. Wooden Gothic font cover, with 8 gables. A small C12 font found in 1896 stands under the tower with crude round bowl on round shaft on square base of upturned cushion form, on wider square plinth with chamfered corners. Oak tower screen preserves the remains of the C15 chancel screen: three bays with massive chamfered and stopped panelled lower part, open arched upper part with crocketted attached pinnacles, vine-carved spandrels and top beam. Heavy oak pulpit of 1924, to R. & M. Jefferys, by Harry Hems of Exteter, with ogee blind tracery and crockets to paired panels, four statues at angles under crocketted canopies, on octagonal plinth. Oak steps up with traceried roundel panels. Brass eagle lectern to David Lewis died 1917. C17 altar table preserved under the tower, also village stocks of 1798. Chancel screen of 1925 to D. & E. Jefferys of Neuadd, also by H. Hems, late Gothic style, five bays with delicate traceried heads to openings and crested beam. Oak altar rails with open panels framed with neo-Jacobean scrolls. Oak stalls with poppyhead finials and open frontals with shouldered upper panels over quatrefoil roundels. Carved Gothic oak altar table of five panels with centre Lamb of God flanked by corn, vine, lily and passion flower, probably early C20, in memory of W. B. Evans. Nave pews with panelled backs similar to pews at Llanfrynach and shaped bench ends.
Incised stones: Replica in plaster of the Llywel stone, a large slab found in 1878 on the Trecastle to Glasfynydd road about to be used as a gatepost. It was covered in remarkable incised patterns possibly of C8 date. On the back are Ogam markings and inscription 'Macutreni saliciduni' presumably C5-6. The original now in the National Museum of Wales. Also the Aberhydfer stone, marked with Oghams and letters possibly 'Taricoro'..
Memorials: In tower S wall slate plaque to Howel Bevan of Llwynycarw died 1761 and the Rev. John Powel died 1801. W wall slab with relief foliate cross and eroded lettering. Nave N marble gabled memorial with oval plaque to John Evans, banker, died 1876 (matching memorial to T. Evans opposite), grey and white marble plaque to a daughter of the Rev L. Llewellyn, died 1813, by Wood of Bristol; marble plaque with urn on grey marble, to David Lloyd of Blaenclydach died 1808, also by Wood. S wall to David Bevan 1868, Thomas Evans of Castle House died 1865 by A. Evans of Sennybridge. Mary and Watkin Lloyd of Trecastle died 1845 and 1855, by G. Hay of Brecon. Chancel N incised plaque to S'bil wife of Howell Morgan, daughter of Thomas Jeffreys of Ceven Rossan died 1600; marble neo-Grec plaque to David Jeffreys of Trecastle died 1852 and his wife died 1856 by Edwardes, Edwards & Co of London and similar plaques to Rees Jeffreys died 1900, by A. Evans of Sennybridge and D.T. Jeffreys died 1923; large white marble ornate Gothic memorial to Lewis Powell of Maespoth and Clynmeddig, died 1867, with crocketted finials and column-shafted pointed arch with stellar cusping by Joseph Chapman of Frome, Somerset; Gothic memorial to Catherine Jeffreys Powell of Glanwysc died 1932 and sisters died 1907 and 1927. Chancel S marble plaque commemorating the works of the Rev. Lewis Price including the National School and house 1863, Vicarage 1865, restoration of the church and rebuilding of Llywel schoolroom 1869, Pentrefelin National School and house 1872-3, purchase of site for Pontarhydfer church 1876, and restoration of the church tower 1877-8. Memorial to Edward Jeffreys of Beyleye Cwmdwr died 1642 and Watkin Jeffreys died 1684.
Stained Glass: Big 4-light E window with two panels of Baptism and Crucifixion and small outer panels of Evangelist symbols, to Lewis Powell MD 1872. Bright colours, by Cox & Sons. Chancel N 3-light to Dr J. Jeffreys Powell, SS Llywel and Luke and Crucifixion, mid to later C20 by Luxford Studios of New Barnet.