In this paper in situ dynamic test results on a long span timber footbridge are reported. As a result of evident flexibility of the structure not taken into account for during the design phase, the test engineer required a dynamic test just after footbridge concluding, with the aim to get realistic values of the main dynamic performances so as to compare them with numerical models. By means of a refined numerical model, it was so possible to analyse the structural performance under many environmental loads, namely wind, live load and earthquake.