Before suburbanisation the main drive leading to Belsize House (c.1500-1853) corresponded with the line of the present Belsize Avenue. The house itself had a substantial courtyard form and was surrounded by extensive gardens with views over London to the south. The surrounding land was in agricultural production with a combination of arable land and pasture supplying the capital.

Belsize Avenue was the scene of 18th century traffic jams when the grounds were used as a pleasure garden. Until 1835 a five-barred gate closed the east end of Belsize Avenue.

In 1852 Charles James Palmer, a Bloomsbury solicitor, bought the lease of Belsize House, with the intention of building. The Dean and Chapter of Westminster decided to retain control of the Avenue, keeping it undeveloped and so Palmer had to change his building layout plans.

A temporary fire station was established in Belsize Avenue during 1869, and in 1870 the Dean and Chapter finally gave Belsize Avenue to the parish of Hampstead, on condition of the vestry planting new trees as the old ones were failing.

Building, mostly by William Willett, finally proceeded on both sides of Belsize Avenue from 1871. The housing that still lines Belsize Avenue derives from the desire to develop large scale houses, set well back from the road retaining an avenue of trees along its length.

In her 1902 book "The Fascination of Hamsptead", Geraldine Mitton says: "Belsize Avenue is a park-like road, from which on the south side stretch the meadows of Belsize Park. Large elm-trees of great age throw shade across the road, and seats afford rest to those climbing the ascent to Haverstock Hill."

Due to a slump in this value of style of housing, houses in Belsize Avenue halved in value between the 1880s and the 1920s and 1930s.

Price have recovered somewhat!