Firefighters were called to the former Harcourt Sands holiday park after a chalet was seen to be on fire.
Crews were called to Puckpool Hill just after 7.30pm.
On arrival, an empty chalet - measuring 4m x 6m - was well alight, along with an adjacent bonfire.
Two appliances from Ryde were called to the derelict site, which has been sitting empty for several years.