Interior of nave is mostly rendered with exposed dressings; larger areas of unrendered masonry in upper nave; E end is ashlar. W narthex/lobby under tower with Norman arches, taller to W doorway and very tall tower arch to nave. Late medieval font, a shallow bowl with quatrefoil mouldings, tall stem on a battered plinth with supporting slender outer mouldings; C19 tall carved wooden font cover enriched with quatrefoils and crockets; benefaction boards. Ringing chamber in gallery above with some fine wall monuments. 4 bay Norman nave with plain round arches to aisles with set back inner arches, plain imposts with no capitals. On N side plain triforium arches and larger clerestory arches; on S side paired triforium arches with dividing colonettes, single plain clerestory lights. In NW chapel, the Worcester tomb to Henry, second earl of Worcester, Lord Herbert of Chepstow, Raglan and Gower died 1549 and second wife Elizabeth; a freestanding monument with two painted effigies, two round-headed arches to the long sides with half-round columns with plinth and cartouche panels below and an entablature above with rosette frieze with moulded pyramidal end finials and central heraldic cartouche. Royal Arms of 1841 on canvas adjacent. Flat boarded wooden ceiling, part in coffered panels. Stained glass in SE nave of 1870s by Lavers, Barraud and Westlake, SW by Samuel Evans c 1896. Most glass which is not figurative is of grisaille-stype. SE nave arch is open leading to S transept chapel with small Norman bowl font. Nave has wooden floor with red-tiled aisles and is furnished with chairs.
Crossing has footings of huge Norman piers at N. The rebuilt transepts have tall quatrepartite columns, two deep to S creating a double transept arcade: pointed arches, stiff-leaf capitals, full height arches to left forming recess with wall monuments; organ to right with notable Gothic case. Vaulted wooden ceilings supported by piers and corbels, the section over nave is fan-vaulted. Recess in Norman masonry between S nave and S transept. In S transept a fine Jacobean monument to Thomas Shipman, Richard Cleyton and Margaret who was married to both, she died 1627. It comprises a group of 3 figures in a square-headed recess, the woman recumbent and the two men kneeling, small-scale children below - 2 male and 10 female; the recess framed by columns with heraldic cartouche above flanked by pyramidal finials; marbled finish, repainted. A number of other good quality late C18/early C19 wall monuments, some by Bristol monumental craftsmen. C18 clock mechanism made by William Meredith 1775-1791, Chepstow clock-maker. Stone pulpit in Geometric style by Coates Carter 1891. N transept has a chapel with panelling commemorating world war dead.
Chancel, 5 steps up, has full height arches to left forming a recess with wall monuments; to right the organ with notable Gothick case of c 1800. Edwardian choir stalls with lamps, encaustic tiled floor. 5 steps up to sanctuary, 2 sanctuary windows to each side. Very long polychrome altar and large polychrome reredos of 1922 by Coates Carter, dedicated to women of Newport and Gwent for service in the Great War; stained glass behind. In N wall a reset aumbry, medieval; with trefoil-headed niche, pedimented moulding and large face stops. E window of 1896 by Lavers and Westlake.