Horses are herd animals, and their social environment strongly determines their ability to cope with stressful events, their mental health and welfare. Humans are part of horses social environment and the relationship between horses and humans is of interest as horses are part of people’s life in many ways, as sport partners, companions and aids in therapy. It is important to know more about horses’ physical and psychological needs in order to be able to better fulfil these. We wanted to gain more knowledge on human to horse emotional contagion, by investigating the effects of a handler’s familiarity on the stress response of 16 horses that were guided through a scary corner and that performed a ridden novel object test.