Tower has pointed barrel vault and pointed hollow-moulded C15 door to stair with chamfered stops to moulding. Tall pointed C15 tower arch. Upper stage of tower was 2 floors, perhaps priests room under ringing chamber, but the upper one has a fireplace. Nave W end has large pointed loft door over tower arch (access to upper chamber). Eleven bay nave roof, possibly C17, has 12 close-spaced broad collar trusses with arched braces, straight braces and wishbone struts over collars. Four rows of purlins. Nave E truss has timber-framing infill, chancel has pine boarding of 1880. Roofs restored 1913. Nave and chancel have plastered walls with faint traces of wall-paintings. Numerous square holes possibly put-log holes found and opened 1913.
S wall has one square hole to right, then cusped lancet in segmental-pointed rough reveal, C19 reveal to 3-light window, another square hole. S door has earlier C19 inner door with reeeded keystone to timber surround, then another square hole, then 1913 timber lancet in C12 narrow light with segmental pointed reveal, another square hole, a segmental-pointed former door to rood stair with renewed head and then the other C19 3-light window inserted in recess of former rood stair.
N wall has square hole to left, segmental-pointed reveal to part-blocked window, another square hole, jambs of blocked medieval N door originally with hollow moulded pointed surround with chamfered stops, broken for 1880 2-light window. Another square hole. a segmental-pointed blocked opening, fragment of wall-painting with chevron pattern, a fragment of a medieval tomb slab, a fragment of medieval carved wood with half a tiny carved face over low Tudor-arched door to vestry. Large 1880 broad segmental arch to organ chamber with vestry. One step to chancel with tiled floors and 1880 roof panelling in 8x6 panels, shallow cornice with bosses. Chancel has evidence that floor has been raised in that E wall piscina and remnant of earlier E window are at floor level. Sills and part of splays visible of 2-light E window, which Caroe thought base of a pair of late C12 to C13 lancets and reconstructed with rounded jambs and centre pier and stone voussoirs to low cambered heads. Fragment of C17 painted text to right over a square hole. N wall has C13 tomb recess or Easter sepulchre with low pointed head, and second recess to left, damaged by insertion of a square headed tall recess. A line of quoins above may be an indication of a lost N transept. A pointed top of a lancet window is visible to right over 1913 single lancet.
S wall has blocked S chapel arch with plain chamfered imposts, to right is jamb of a blocked opening over a red stone 2-light window with another piece of straight stonework in wall to right and 1913 deep-set rectangular leaded narrow light above.
Fittings: C15 red conglomerate stone font, octagonal bowl, chamfered beneath, on C20 stem. Altar table and credence C17. Pulpit 1922 by Caroe, timber octagonal on tapering base. Organ rebuilt 1880 by Bevington & Sons of Soho, with painted pipes, in Gothic case. Later C19 chancel stalls with cusped arcading to fronts. Brass eagle lectern c1896.
Monuments: In S porch E side a delicately lettered early C19 oval with no name but 'Je remets mon ame en ta main car tu m'as rachete', and red stone plaque to Thomas Powell died 1787. E side eroding plaque to Rev John Williams, Pantycelyn, died 1828, with motto 'A sinner saved' and note that this line was inserted at the request of the deceased. Plaque to right to Thomas Jones of Ystradwallter died 1762 and wife died 1767, with good lettering. Nave N above vestry door marble plaque with urn to Rev W Thomas of Pantyrhedyn, died 1853, by D. Beynon. Chancel S brass to Thomas Jones of Llanfair Grange, died 1901, detached plaque to William Williams of Pentwyn, excise officer, died 1799, plaque to Morgan Williams of Pentwyn, gent, died 1790, marble plaque to Jane Gwynne died 1802, and plaque to Maryanne Gwynne died 1818. Plaque to William Leeves of Tortington Place, Sussex, died 1870. N plaque to Mary Anne Gwynne died 1818 and to Col Sackville Gwynne of Glanbran died 1836 and his wife died 1888.
Stained glass: tower W window by John Petts to Major W Stewart of Llanfair House, 1972, sun in vibrant colours. Nave S fourth window has c. 1880 glass of Christ healing sick, in style of Hardman. Chancel S 2-light has glass by John Petts of 1965 to J L Stewart, killed 1940 with St George and dragon with swastika (the design said to be not by Petts). Narrow window set low to left has glass given by John Petts 1972 with letters 'CARDI'. Chancel N small single light by Kempe & Co c1924, St David, and 2-light to right by Kempe & Co 1931, Feed my lambs. E window of three lights, c. 1924 by Kempe & Co, Crucifixion with Rev Rhys Prichard and Rev William Williams, the figures on clear grounds.