Investigators said that sometime late Saturday or early Sunday, the vandals used rocks and other items to shatter glass mirrors and doors.
They also clogged toilets and smashed sinks.
"I'm disgusted that someone would so callously destroy the restrooms at our flagship park," said Parks, Recreation & Cultural Resources Director Ruben Wall. "This malicious act will not be taken lightly."
Wall said repair costs will likely run into the thousands of dollars.
The restroom will remain closed while repairs are made.
Anyone with information concerning the vandalism is asked to call the Wake Forest Police Department at (919) 554-6150. Callers may remain anonymous.