The ambient movement of three multi-storey cross-laminated timber (CLT) buildings have been measured and used to determine natural frequencies, mode shapes and damping ratios. This information, obtained by a simple, unobtrusive series of tests, can give insights into the structural performance of this form of building, as well as providing information for the design of future, taller timber buildings for dynamic loads. For two of the buildings, the natural frequency has been related to the lateral stiffness of the structure, and compared with the stiffness based on simple calculation. In future tall timber buildings, a new design criterion is expected to become important: deflection and vibration serviceability under wind load. Design standards give techniques for prediction and mitigation of wind-induced movement, but require an estimate of the mass, stiffness and damping ratio of the structure to make an accurate prediction. For multi-storey timber buildings there is no empirical basis to use for damping estimation, and there is little information for stiffness. This study therefore provides an insight into the modal properties for lateral vibration of multi-storey CLT construction which could inform the design of taller buildings in the future.