About three-quarters of an acre burned in an area east of the park's clubhouse around 2 a.m., Assistant Chief Tom Siragusa said.
The fire was under control by about 2:30 a.m., Siragusa said.
No one was injured in the blaze, and the cause remains under investigation.
The fire did not damage the stage area where weekly summer concerts are held, Siragusa said.
The park is located at Sloat Boulevard and 19th Avenue.