Northwood House and Park once formed part of the Mount Edgcumbe estate. In 1793, Mount Edgcumbe property, comprising a house called Belle Vue "a house, 2 coach houses, 4 stables and 4 gardens", was bought by George Ward and renamed Northwood Park.

George Ward was the son of a retired City merchant and a director of the new East India Docks. William Arnold (Collector of Customs for Cowes) had known George in London and told him about the sale of the Mount Edgcombe estate. Having bought Belle Vue, George began to buy up land in Cowes and surrounding areas and the estate subsequently passed down through the family.

In 1813 George Ward represented Northwood on the Highways Commission and when it was decided two years later that two turnpikes were to be erected at West Cowes, Ward built the toll house at Debourne Bunny - the Round House - which he let to the Highways Commissioners for 20 years. In 1967 the County Surveyor decided The Round House was a traffic hazard and ordered its demolition but it was saved after a public outcry.

Also at the Park's south-west entrance, opposite the Round House, stands the picturesque though modified Debourne Lodge. Both were probably designed by George Repton, an architect son of Humphrey who worked for Nash. The original carriage drive to Northwood House entered the park beside this lodge and went through what is now an estate of houses towards a classical walled forecourt and the Rotunda entrance to the House.

The grounds were landscaped soon after their purchase, and modified again when the house was rebuilt in 1837 to a design by James Pennethorne (an adopted son of Mrs Nash who became Nash's business successor). The modern Ward Avenue formed the boundary between the pleasure garden and the park. The kitchen garden was where the Park Court flats now stand - an old wall and a fig tree survive, and an ice house can still be seen in the Park.

By 1858 William George Ward of Northwood House was said to own four-fifths of Northwood Parish - which at that time covered the whole of West Cowes, Northwood, Gurnard and stretched as far as Thorness and Parkhurst Forest - as well as the remarkable Weston Manor in Totland. William George was a rather unlikely friend of the poet Alfred Lord Tennyson, who at William George's death in 1882 wrote of him:

Farewell, whose living like I shall not find,

My friend, the most unworldly of mankind.

Northwood House was at the centre of late Victorian high society. In 1871 a Grand Bazaar and Promenade Concert was held in the grounds with the proceeds going to the National Hospital for Consumption in Ventnor (now the Botanic Gardens). This was an impressive gathering and guests included the Imperial Prince and Princess of Prussia accompanied by Lady Churchill and many others in Society, who entered the Park by the Castle Hill ('Nunnery') Steps. Royal Yacht Squadron Balls were also held there in the 1880s, attended by the Prince and Princess of Wales.

At the turn of the 20th century the house was turned into a nunnery for a short time and during the First World War it was a VAD hospital for convalescing soldiers. In 1929, Captain Herbert Joseph Ward, a JP and long-time Chairman of the Council, gifted the estate to Cowes Urban District Council - 'the grounds for use as pleasure gardens for the people of Cowes and the house as municipal offices'. On 4th September 1929, H.R.H. Princess Beatrice, Royal Governor of the Isle of Wight and the youngest daughter of Queen Victoria, accepted from Captain Ward the deeds to Northwood House and grounds. On this sunny, autumnal day, under the gaze of a large gathering of townspeople, representatives of the civil and social life of Cowes and of various Island public bodies, the Princess handed the deeds over to Mr. F. W. Beken, chairman of Cowes Urban District Council, and Northwood House Charity was born.

For many years after this, the house was held in trust by the Council - subsequently Medina Borough Council, the Isle of Wight County Council and most recently the Isle of Wight Council - and occupied by various council departments. Under the 1929 Deed of Gift, Northwood House was to be maintained for the use of the Council as offices, for the housing of caretakers and to let rooms suitable for meetings, concerts and other entertainments. Northwood Park was left to the residents of Cowes for recreation and pleasure. There was also provision for a fee paying car park in the neighbourhood of Park Road, which was duly established. Northwood House Charity was formally registered with the Charity Commission in 1978. The register office was moved to part of the downstairs rooms at Northwood House by the Isle of Wight Council in 2004.