This paper describes a deployment of a wireless monitoring system on a timber footbridge. The goal of the monitoring was to provide: information about vibration amplitudes during operation and to track the changes of natural frequencies with temperature changes. The sensor nodes were equipped with an accelerometer and a temperature/humidity sensor. The vibrations were recorded permanently. The acquired raw data was processed in the sensor nodes to compute the envelope of the vibration amplitudes and the dominant peaks of the Fourier spectrum. The deployment demonstrated that monitoring the dynamic performance of a structure with a wireless sensor network is technically feasible and economically effective. The data quality matched the requirements. The wireless monitoring system worked for about one year with high reliability. Battery replacement was necessary only once after 6 months of operation.