The church of St. Peter consists of a chancel (40 ft. by 16 ft.), north chapel (40 ft. by 15 ft.), south chapel (39½ ft. by 15½ ft.), nave (62 ft. by 19 ft.), north transept (23½ ft. by 16 ft.), south transept (23½ ft. by 16 ft.), north aisle (59½ ft. by 17 ft.), south aisle (59½ ft. by 16½ ft.), west tower (14 ft. by 14 ft.) and south porch. The walls of the porch, the east wall of the chancel and parts of the tower are faced with ashlar, and those of the rest of the church are coursed rubble. The roofs are covered with lead.

The church is mentioned in the Domesday Survey (1086). It seems to be probable that an early church, possibly with a central tower,  was enlarged by the addition of large transepts in the middle of the 13th century, and that in the last decade of the century the remainder of the church was rebuilt and further enlarged; of this period are parts of the walls of the chancel and the two side chapels, and those of the two aisles. Apparently, when this enlargement was made, the old arches between the transepts and the aisles were not altered, but the widened aisles were opened to the transepts by means of narrow arches (which still remain) on the outside of the older ones, which were destroyed in the 15th century. About forty years later the east wall of the chancel was again rebuilt and a large window inserted in the end of the south transept. Towards the middle of the 15th century the west tower and spire were built within the church, possibly to replace a central tower, for shortly afterwards the nave arcades were rebuilt together with the arches between the aisles and the transepts, and the clearstory was added. About the same time the porch was rebuilt. The chancel with its side chapels was thoroughly restored in 1902–3, the nave in 1904, the north transept and aisle in 1908, and the south transept, aisle and west tower and spire in 1909–10.

The late 13th-century chancel has a five-light east window, of c. 1335, with flowing tracery in a twocentred head, on each side of which is a late 14thcentury ogee-headed niche. In the north wall is an original arcade of two bays having pointed arches of two chamfered orders on a column of quatrefoil section with moulded capital and base, a similar attached half-column at the east respond and a moulded corbel on the west; and a rectangular locker. In the south wall is an arcade of three bays similar to those on the north but the columns have filleted shafts and the mouldings of the capitals and bases are rather richer, and the responds have shafted corbels resting on carved heads. The clearstory has, on each side, three original two-light windows with trefoiled ogee lights under a segmental head. The original roof, much restored, has moulded beams and purlins, and the jack-legs rest on shafted corbels rising from the string-course below the windows. The very late 13th-century chancel arch is two-centred, of two chamfered orders resting on semi-octagonal moulded corbels with circular conical shafts. On the wall above the weatherings of the earlier chancel roof remain.

The late 13th-century north chapel has in the east wall a window of three graduated lancet-lights under a continuous label with a little simple tracery in their heads; a rectangular locker; and a 15th-century bracket. In the north wall are two similar three-light windows and a 15th-century four-light window with a four-centred head. In the eastern bay of the south wall is a piscina with trefoiled head and octofoiled basin; and graduated triple sedilia with trefoiled heads under a triple-gabled hood-moulding. In the west wall is a late 13th-century two-centred arch to the transept, the lower order resting on moulded corbels. The roof is modern but includes a few old timbers, and the jack-legs rest on corbels carved with grotesque heads.

The late 13th-century south chapel has in the east wall a three-light east window of c. 1335, having flowing tracery in a two-centred head; and two brackets. The south wall has a three-light window similar to that in the east wall; two original threelight windows with pierced spandrels in pointed heads; a piscina with a two-centred head and a mutilated round basin; another piscina, farther east, with cinquefoiled arch under a square head, and a shovelshaped basin; and two rectangular lockers. In the west wall is a late 13th-century arch similar to that in the north chapel. The roof also is similar to that of the north chapel.

Externally the east end of the church is very fine; the chancel has a low-pitched gable with a plain parapet, and is flanked by two late 14th-century buttresses with gabled tops; the parapeted gable-ends of the side chapels are bent about half-way up and are finished at a lower pitch, and have carved animals at the corners, a collared bear on the north and a crocodile on the south.

The late 15th-century nave has an arcade of four bays on each side, having two-centred arches of one moulded and one chamfered order, resting on narrow piers formed by the continuation downwards of the outer orders of the arch between two attached semioctagonal shafts with moulded capitals and bases, and having on the sides next the nave and aisle small attached shafts, those in the nave carried up to support the jack-legs of the roof. At the north-east corner is a large rood-stairs turret much restored, with a modern doorway to the loft; and at the south-east corner is a blocked square-headed opening in the arcade wall. The clearstory has on each side four three-light windows with four-centred heads. The roof is modern.

The mid 13th-century north transept has in the east wall a single-lancet window; a late 13th-century piscina with trefoiled head and quatrefoiled basin; a rectangular locker; and an almost destroyed bracket. In the north wall is a late 13th-century three-light window with simple tracery under a segmentalpointed head. In the west wall is a single-lancet window with its southern internal splay altered; a narrow late 13th-century arch to the aisle having three orders, one moulded and two chamfered, resting on an attached triple shaft on the north and a perfectly plain 15th-century jamb on the south; and a wide 15th-century four-centred arch, also to the aisle, of two chamfered orders springing from the pier of the nave arcade on the south and from a plain respond with a small attached shaft on the north. In the south-east corner is the lower door to the rood-stairs. The jack-legs of the modern roof rest on a 13th-century corbel carved with foliage and on two 14th-century carved heads.

The mid 13th-century south transept has in the east wall a single-lancet window. The south wall has a mid 14th-century five-light window with reticulated tracery in a two-centred head; a cinquefoiled-headed piscina with circular basin; and a locker with pointed head. The west wall has two arches to the aisle similar to those on the north, except that the earlier arch rests on an attached semi-octagonal shaft instead of a triple shaft. The jack-legs of the modern roof rest on two 13th-century carved heads.

The late 13th-century north aisle has in the north wall two original three-light windows with segmentalpointed heads; a late 15th-century three-light window with a four-centred head; an original doorway with a two-centred arch of two continuous hollowchamfered orders; and a plain recess with pointed head. In the west wall is a late 15th-century threelight window with a four-centred head.

The late 13th-century south aisle has in the south wall an original window of three graduated lancetlights under a continuous label; two 15th-century three-light windows with four-centred heads; an original doorway with a two-centred head of four moulded orders, the innermost of which has been trefoiled but the cusps are now broken off, resting on two detached and one attached jamb-shafts on each side, all with moulded capitals, bands and bases. The west wall has a window of three lancet-lights similar to that in the south wall.

The late 15th-century west tower stands on three arches within the church; all are of two orders, the outer orders have wave-moulded chamfers continued down the responds, and the inner orders are carried on semicircular attached shafts with moulded capitals and bases. The west doorway has a four-centred arch with continuous moulded jambs. The west window is of three-lights with tracery in a twocentred head. In the stage above is a single-light window under a square label, in the west and south walls; and the third stage, which is otherwise blank, has a similar window in the north wall. The belfry windows are three-lights with transoms and depressed four-centred heads. The tower has clasping buttresses at the angles and is finished with an embattled parapet below which is a string-course with carved gargoyles at the angles and in the centre of each side. At each angle is a crocketed pinnacle with a flying buttress, pierced with quatrefoils, to the base of the spire. The crocketed spire, which rises from behind the parapets, has two tiers of spire-lights on the cardinal faces, the lower two-lights and the upper single-lights.

The late 15th-century south porch has a fourcentred outer archway of two chamfered orders, the lower order carried on semicircular attached shafts with moulded capitals and bases. Above the arch and on either side of it are niches having moulded brackets and crocketed projecting ogee heads. In the east wall is a two-light window with a four-centred head, but the mullion and tracery are missing. The walls are finished with plain parapets; on the south gable are three carved beasts, viz.: a yale between a lion and a dog. On the wall of the south aisle the marks of the roof of an earlier porch remain.

The late 13th-century font has an octagonal bowl with square sunk panels and a hollow-chamfered underedge, on a modern circular stem with moulded capital and base.

There are six bells, inscribed: (1) J. Taylor & Co. Founders Loughborough 1881. Praise God in his Sanctuary. This bell was added to the ring a.d. 1881. John and Sarah Nickolls Benefactors Fred. J. Moule M.A. Vicar; (2) J. Taylor & Co. Founders Loughborough 1881. Haec est domus Dei et aula coeli Jonath. Styles Vicar 1721. This bell was recast 1881. John Nickolls Benefactor; (3) Domus mea est domus orationis 1721; (4) Gloria Deo excelsis 1721; (5) J. Taylor & Co. Bellfounders Loughborough 1881. Hen. Clinton Comes Lincolniensis Benefactor. John Child Simon Brown churchwardens. Hen. Penn founder 1721. This bell was recast a.d. 1881. John Nickolls Benefactor. J. Turner J. W. Moore churchwardens; (6) Memento mori. Joh. Proby armiger manerii dominus Benefactor 1721.

In 1552 two bells were removed from the church by Mr. Connie ‘for my Ladie Elizabethes grace,’ of which one was returned to the parish to ring in case of fire; from which it would seem that the church had only two bells and they were left with only one.  In 1709 there were four bells;  by 1721 one of these was cracked,  and this seems to have led to the recasting of all four by Henry Penn, of Peterborough, and the gift of a fifth bell. In 1853 one bell was broken and another cracked.  These were presumably the old treble and the old fourth bell which were recast and a new treble added in 1881. The fourth bell, which had been cracked since 1928, was recast, and the whole peal rehung in 1931.

Under the chancel arch is a 15th-century oak screen of six bays with open traceried panels above and close lower panels bearing remains of painted decoration. The covings and loft are modern and carry the organ. The chancel stalls are mostly modern but include two late 15th-century desks having fronts with tracery panels, and shaped ends with carved poppy heads; two other bench ends with poppy heads; and several other portions.

The oak pulpit, dated 1631 and bearing two shields with initials ‘H.S.’ and ‘I.P.,’ is hexagonal and panelled in three heights with carved panels and moulded rails, and has a sounding-board with moulded cornice and the initials ‘R.E.’ and panelled frieze; it stands on a 15th-century octagonal coving rising from a moulded and battlemented base.

There are several wall paintings: (a) above the arcade on the south side of the north chapel are 14th-century scenes from the Resurrection, including a standing figure of Christ, Christ and St. Mary Magdalene, the road to Emmaus and the Incredulity of St. Thomas, and remains of floral decoration and powdering of cinquefoils; (b) on the north and south walls at the east end of the nave are early 16th-century fragments apparently flanking a Doom over the chancel arch, on the south figures rising from graves, floral decoration and black-letter inscription; (c) on west wall of the nave, 17th-century painting with Prince of Wales’s feathers and motto within a garter surmounted by a crown, figures of a man in Roman armour, another in a long cloak, a gravedigger and a skeleton, with texts; (d) on the north wall of the north transept, late 13th-century band of foliage.

In the north chapel is the matrix of a 14th-century brass with foliated cross having demi-figure of a priest in the head, and a marginal inscription.

In the north wall of the north transept is a projecting stone with sunk panel having a pointed head and two arms holding a heart; a cylindrical wooden box containing a heart was found behind this stone in 1842, and is now preserved in a modern recess near it; the heart is supposed to have been that of William de Yaxley, Abbot of Thorney, who founded a chantry here in 1291, and died in 1293.

In the north aisle are two loose fragments of a late 13th-century effigy of a priest in mass-vestments.

In the churchyard are a broken stone coffin and lid and eleven pieces of coffin-lids, most of them with foliated crosses and two with the double-omega ornament.

There are the following monuments: in the chancel, floor slabs to Mrs. Elizabeth Huddle, d. 1758; John Child, d. 1790. In the north chapel, to Capt. John Draper, R.N., d. 1813; the Rev. Charles Lee, Vicar, d. 1868, and Harriette his wife, d. 1886; Charles Langford, killed in South African War, 1900; and floor slabs to Arthur Lee, d. 1842, and Edward Henry Lee, infant sons of the Rev. Charles Lee, Vicar. In the south chapel, to Thomas Squire, d. 1759; John Newton, late of Spaldwick, d. 1797; Capt. William Taff, d. 1797; Martha Smith, d. 1801; John Child Newton, d. 1803; William Child senior, d. 1813, Susannah wife of his son William, d. 1814, Elizabeth his wife, d. 1820, and William their only son, d. 1825; Susannah (Child) widow of George Paillet, d. 1822, George Paillet, d. 1775, and Susannah Paillet their daughter, d. 1842; Isaac Field, d. 1832, and John Child Field Child, d. 1832; Mary wife of John Newton, d. 1852; and Elizabeth H. Hopkins widow of Edward Jarvis Hopkins, R.N., d. 1870; floor slabs to Elizabeth wife of Thomas Squire, d. 1736, and Edward their son, d. —; Thomas Squire, d. 1759; Peter Lamb, d. 1794, and Mary his wife, d. 1794; J.N. 1797; William Child senior, d. 1813 (all as above); Isaac Field, d. 1832, and John Child Field Child, d. 1832; and glass window to the Squire family, erected by William Squire, 1849. In the nave, floor slabs to Rebecca wife of Thomas Bowker, d. 1752; Mary relict of John Barnes and late wife of John Catlin, d. 1769, and Jeremiah Askew her grandson, d. 1829; Ann Reesby, d. 1799; — daughter of — and Ann Waite, — — and Elizabeth wife of Henry Green, d. —. In the north transept, floor slab to John son of John and Phyllis Chambers, d. 1798. In the south transept, floor slabs to William Frashe, d. 1699; — Faux, d. 1808; Robert Faux, d. 1812; William Sharman, d. 1813; Margaret Faux, d. 1817; and Catherine daughter of Francis Faux, d. 1832; and glass window to the Rev. Edward Howard Brown, formerly Vicar, d. 1925. In the north aisle, floor slabs to John Draper, d. 1813; Freeman Bowker —; — wife of — Bowker —; Phyllis wife of John Chambers, d. 180(?); and John Chambers, d. 1817. In the south aisle, War Memorial, 1914–18; and floor slabs to Thomas Bowker, d. 1792; and — [V]illy, d. 1813.

The registers are as follows: (i) baptisms, marriages and burials, 13 November 1653 to 27 December 1812, marriages end 25 February 1754, bound in a modern cover; (ii) the official marriage book, 18 June 1754 to 19 November 1812.

The church plate consists of a plated chalice engraved ‘Calicem Salutaris accipiam et nomen Domini invocabo’; a plated standing paten engraved ‘Agnus Dei qui tollis peccata mundi da nobis tuam pacem’; a plated flagon engraved ‘Pascha nostrum immolatus est Christus’; a plated alms-dish engraved ‘Benedicamus patrem et filium cum Spiritu,’ and inscribed ‘To the Glory of God. Presented by the Revd. Charles Lee (Vicar of Yaxley) and his wife as a memoriam of their daughter Henrietta Helen Lee, obiit Jany. 16th 1867.’