Animals are commonly believed to detect human emotions through smell, in link with the primitive and ubiquitous characteristics of chemoreception. Indeed, the brain areas dedicated to odor processing are among the oldest structures in mammalian evolution, and chemosignals may play a role in interspecific communication. However, few studies have conclusively demonstrated that animals can perceive human emotions through smell. To determine whether horses can discriminate between human odors of fear and joy, a habituation-discrimination protocol was used. Horses were exposed to sweat odors from humans who declared they had experienced fear or joy while viewing a comedy or a horror film, respectively. A first odor was presented twice in subsequent trials (habituation), and then the same odor and a novel odor were presented simultaneously (discrimination). Both odors came from the same donor. Experimenters presenting the odors or coding the behavioral responses of horses to odors were blind to the condition. Horses sniffed the novel odor more than the repeated odor, indicating that they discriminated between the human odors produced in fear and joy contexts. Moreover, asymmetric nostril use and differences in habituation speed further imply differences in the emotional processing of the two odours by horses.