St John’s church forms part of the hamlet of Northwood which is situated to the west of the Medina estuary. Northwood church consists of a W tower, nave, N and S aisles of four bays, and a chancel, with the vestry to the north and organ chamber to the south. The nave arcades have pointed arches, with the S aisle entered through a round-headed doorway with chevron around its head. The small W tower and spire were added in 1864 and the S porch is of a similar date (Lloyd and Pevsner 2006, 197). The Romanesque features are the S doorway and the nave arcades.

Northwood was not itemised in Domesday Book. Northwood was one of the chapels dependent on Carisbrooke church 1193x1217, with the possession of the chapel of Nortwuda having been confirmed by Pope Lucius III, 1181x1185 (Hockey 1981,4,43). An annual payment of 30 marks was being made by Northwood chapel to Carisbrooke church c.1268, which would have been Northwood's contribution towards the pension paid by Carisbrooke church to Lyre Abbey. It would appear that the dead of Northwood were still being taken to Carisbrooke for burial in 1289, when there was a dispute over the payment of a beast for mortuary dues (Hockey 1981, 38, 172, 157). Worsley records that that although Northwood was a chapel of ease to Carisbrooke, since the time of Henry VIII it enjoyed all parochial privileges and was exempt from contributions for repairs to the mother church (Worsley 1781, 231).

Although superficially of similar form, there are significant differences between the N and S arcades of the nave, for example the forms of the plinths and the quirks on the imposts of the N arcade capitals which are not present on the S arcade. It is quite possible that the two arcades were constructed a few years apart.

The font which had been buried in the churchyard, dug up in 1954 and now displayed in the porch, is not dateable due to the lack of any adornment and its dilapidated condition. It is possible that it dates from the 12thc. The total height of the font is 0.63 m, the roughly cylindrical base being 0.28 m high and the roughly cylindrical bowl 0.25 m high. The external diameter of the bowl is 0.62 m.