Both humans and animals appear to be sensitive to cues displayed by each other while interacting and adapt their behaviours accordingly. However, very little is still known about the relevant elements that have to be considered when humans interact with horses. Here we investigated whether humans’ emotional state had an impact on horses’ heart rate and level of obedience in a simple leading task. Professionals (6 women, 2 men) and non-professionals (3 women, 3 men) were asked to lead a horse along a given path. Experiment 1 was performed on 8 professionals and 3 horses kept in natural conditions (site A); experiment 2 on 6 non-professionals and 13 horses, of which 5 from the site A and 8 from a riding school (site B). Humans’ and horses’ heart rates were recorded during the interaction. People also reported a posteriori on their positive (e.g. pleasure) and negative (e.g. fear) emotional states (questionnaire). Women reported on more satisfaction and more intense emotions than men (P<0.05). Interestingly, horses’ emotional states might be related to humans’ emotional states in women/horses dyads: heart rates of horses and women were higher in the site A than in the site B (P<0.05). Level of expertise also seems to be at stake in humans’ emotional states: non-professionals had lower heart rates and expressed less negative feelings (i.e. misunderstanding) than professionals (P<0.05). Horses however showed higher heart rates with non-professionals (P<0.001). These results suggest that horses are able to perceive humans’ emotional states. On-going analysis performed on horses’ behaviours will allow us to explore further the relationship between heart rates variations and the valence of the horses’ emotional states. The results reinforce the idea that knowledge of factors which might impact on humans’ emotions should be promoted, as appropriated emotions might be key elements to prevent accidents.