Nowadays, rail vehicles with superior dynamic performance and higher commercial speeds are required to support the development of rail transport systems. Suspension components play a fundamental role in enabling these new vehicles to meet the higher standards required by today’s market. Among the various suspension elements introduced in high-speed rail vehicles, yaw dampers are one of the most influential. In previous studies, they proved to suppress the tendency of rail vehicles to show bogie hunting by stabilizing the bogie yaw rotation [1], [2]. In particular, it was found that a sufficiently high value of yaw dampers’ stiffness is necessary to avoid this unstable motion [3], particularly related to high conicity conditions. Unfortunately, high values of in series stiffness may also introduce another kind of instability, known as car body hunting, a low frequency hunting motion related to low conicity conditions which can be avoided by decreasing the yaw dampers’ stiffness [3]. Besides stability, yaw dampers also influence the curving performance of rail vehicles, since they introduce an additional steering resistance when negotiating sharp transient curves [4], [5]. Smart passive [4], [6], semi-active [7] and fully active [8] dampers were proposed to improve stability and curving performance of rail vehicles. Nevertheless, most of the applications were examined by means of numerical co-simulations of rail vehicle and suspension models, which were generally reproduced with a certain degree of approximation. In this context, this paper integrates Hardware-In-the-Loop (HIL) tests presented in previous studies [9], [10] to study the influence of yaw dampers on rail vehicle dynamics. This approach allows to minimize the modelling errors by replacing suspension model(s) with physical prototypes. Moreover, HIL can test suspension components in conditions which are closer to the real operating scenarios.