Abstract It is now well-known that, under pedestrian excitation, flexible footbridges can exhibit large-amplitude vibrations that impact their serviceability. In particular, some footbridges of suspended spans have exhibited significant lateral oscillation due to pedestrian–bridge interaction. This paper presents the characteristics of pedestrian-induced vibration of a prestressed concrete beam bridge observed using full-scale measurement. The effect of the pedestrian loading on the oscillation frequency of the bridge, as well as its implication on the mechanism of pedestrian–bridge interaction, is investigated. Based on the understanding of the prototype vibration, a model is developed to enable assessment of the amplitude of footbridge vibration induced by pedestrian excitation.