In this study, a three-dimensional vehicle-bridge coupled model was developed to study the dynamic impact of vehicle braking on bridges. The dynamic responses and impact factors of simply-supported prestressed concrete girder bridges were obtained under the braking of a typical three-axle vehicle model. A parametric study was performed to investigate the effect of several important parameters, including the vehicle braking position, deceleration rate, initial vehicle speed, road surface condition and bridge span length, on the impact factors. In addition, a comparison was conducted between the calculated dynamic impact factors and those specified in the current Chinese bridge design code. The results show that the impact of vehicle braking on bridges increases with the increase of braking force, and braking within the first half span causes greater impact than braking within the second half span. Furthermore, the dynamic responses and impact factors of bridges due to vehicle braking are notably greater than those due to the vehicles moving at constant speeds, and the impact factors may exceed those specified in the current Chinese bridge design code.