Five-bay nave with cusped arch-braces on long wall posts which rest on large stone corbels bearing angels. Smaller alternating arch-braces, more heavily cusped, on foliated corbels at wall-plate level. Five-bay arcade to S aisle with double-chamfered pointed arches on clustered shafts, set diagonally, with ringed capitals and bases. High pointed chancel arch with several orders of chamfers and mouldings, the inner ones supported on short black marble shafts with foliated capitals and ringed bases. Doorway to N side of nave with similar mouldings and attached shafts, containing double wooden doors leading to friary buildings. Above, and lighting the corridor beyond, is a short shallow-arched window. Between and flanking the N nave windows are 7 arched stone recesses containing the stations of the cross in high relief. The remaining 7 stations are to the S aisle.
The chancel has a keel-vaulted roof, boarded and panelled with foliate bosses. A crucifix is suspended from the ceiling and was originally attached to the rood screen. The stone altar is in the centre of the chancel (having been moved from the rear). The table is supported on 4 marble columns with foliate capitals. Panels to rear bearing biblical scenes in relief. There are now choir stalls around the E end. Flanking the E window are marble statues of St David and St Asaph under canopies decorated with pinnacles and crockets. These are by Pugin. Heavily cusped rere arches to windows. Door to L of N side to confessional and aumbrey to far R.
The S aisle has a roof of closely-spaced scissor-braces. To the R side of the entrance is a stone piscina with trefoil-arched head. Shallow double-chamfered arch on short shafts to E, leading to the Lady Chapel which is under a vault beneath the spire. On the R of the archway is a statue of mother and child beneath a canopy with pinnacles. The marble altar table is on red marble columns with ringed capitals and bases. Beneath the table, behind glass, is a reliquary of wooden open-work with 3 sexfoils to the front, under a hipped rooflet with frieze to ridge. In the reliquary are the bones of the Roman martyr, labelled 'Corpus Sancti Primitivi M.' Decorative marble reredos, the central part covered by a banner and flanked by statues under highly ornate canopies.
Large octagonal stone font to W end of nave (by Pugin) supported on circular marble shafts around a central stem and on an octagonal base. Each face of the font bears the emblems of the Evangelists in relief, including winged beasts, angels and foliage. Wooden pews with plain moulded bench ends. Small C20 wooden pulpit to SE of nave, and pipe organ to SW in a fine wooden Gothic-style case, by Henry Poyser, Chester. On the S side of the organ is a fragment of the former baptistery screen.
In the N wall of the chancel is an effigy of Rudolph William Basil, 8th Earl of Denbigh (1823-92), erected by his 2nd wife, Mary. It was designed by Purdie and undertaken by Boulton & Sons. The effigy is under an ornate vaulted and ribbed canopy, the triangular head with crockets and pinnacles, the depressed arched opening with cusping and foliate bosses. Black marble shafts to reveals supporting statues of a man and woman. The front of the tomb has 5 bays divided by black and red alternating marble shafts, each with a trefoiled blind arch. That to the centre bears a coat of arms flanked by symbols in quatrefoils including birds, a cross and a tree. Further R is a sepulchre to Lord and Lady Fielding, consisting of 2 cusped blind arches containing brass tablets inside a frame with Tudor flower enrichment and a triangular head. To the R is a small brass tablet to their daughter, Hilda, who died at 1 year.
Fine stained glass to E window depicting the life of Christ including the Crucifixion. The N nave windows have stained glass bearing saints, by Hardman, 1852. That to the R is dedicated to Thomas and Elizabeth Kent. Stained glass to S aisle windows, mainly C20, that to the W by Harry Clarke 1931-4. Further stained glass in chancel. The church retains a fine collection of High Gothic fittings, including encaustic floor tiles and deeply-coloured stencilled wall coverings.