Kent Fire and Rescue Service was called to Jackey Bakers Recreation Ground in Highfield Road, Ramsgate just after 6pm on Friday evening.
Upon arrival crews found a fire in the changing room of the sports pavilion together with fire damage around the entrance of the building.
Crews used a hose reel jet to put out the blaze.
There were no reported injuries and the building was secured.
The cause of the fire is believed to be deliberate and an investigation is underway.