Tuned mass damper (TMD) is a device mounted in structures to reduce the amplitude of mechanical vibrations. It has been accepted that TMD can effectively control the vibration of the main deck of long-span bridges. However, the unfavorable effect on static characteristics of the increased dead load cannot be avoided if the TMD is installed directly on the main deck. Thus, the damping ratio of these types of bridges still need improvements. In this study, a TMD-type counterweight was designed for reducing the earthquake and wind load–induced displacements at the central span. The counterweight was taken as the mass block in the TMD. The TMD was evaluated through a set of experiments that involved fabrication and testing of a reduced scale model of a single plane cable-stayed bridge. The experiments were performed on the scaled model of the Dongshuimen Bridge in Chongqing, China. Distributed strains at the span length and cables were monitored by a Brillouin Optical Time Domain Analysis fiber optic sensor system. Fiber Bragg Grating FBG sensors, were employed for evaluating the efficiency of the TMD. Results indicate that the TMD had notable effects of reducing the vibration of the main deck and increasing the damping ratio of the bridge.