A robber wearing a gray sweatshirt, hood up, and pointing a revolver, robbed the Mobil gas station at 31 North Ave., behind St. Paul's Church on the Green.
No one was injured, and only a "nominal" amount of cash was taken in the incident, which happened at about 11 p.m. Thursday, according to Norwalk police.
The robber is described as a black male, about 5 foot, six inches tall, wearing dark pants along with the gray, hooded sweatshirt.
A police dog later tracked the robber up France Street in the area of St. Phillip's Church. Norwalk police detectives are investigating.