Officers responded to reports of a robbery at the McDonald's restaurant at 522 El Camino Real at about 9:10 p.m.
A man wearing a Batman mask and false vampire teeth had confronted the manager, demanded cash, and made off with an undisclosed amount of cash from the restaurant's office, police said.
The masked bandit is described as a Hispanic male between 5 feet 10 inches and 6 feet tall, weighing 215 to 240 pounds. He wore a blue hooded shirt and blue pants.
The subject was last seen leaving the area in a silver two-door Honda with a black top. As of 11 p.m., a countywide alert failed to yield any leads on the suspect or vehicle, police said.
Anyone with information related to this robbery is asked to contact Belmont police investigators at (650) 595-7400.