Attribution of emotions to horses, as well as understanding how environmental factors may influence such states, may influence owners' and caretakers' attitudes toward horse welfare. This, in turn, may influence how they manage and treat their animals. The aim of this study was to explore the views of Brazilian horse owners and caretakers regarding horse sentience, the contexts or events that may elicit different emotions, and the behaviors they believed to be an expression of these emotions. Survey participants were recruited and invited to participate online through vehicles with national coverage. The questionnaire obtained demographic information of the participants, a closed question asking participants to state their belief in horses' emotions, and two open questions requesting, respectively, a situation in which participants believed their horse had expressed pain and other emotions quoted in the questionnaire. Participants (412 men and 275 women) identified themselves as owners (81%), horse riding instructors (8%), horse centers' administrators (5%), veterinarians, or animal scientists, including students and professionals (6%) and most (63%) as experienced in the equestrian world. Most participants believed that horses have full capacity to feel pain (94%), fear (92%), and joy (77%), and some that horses have full capacity to feel boredom (65%) and jealousy (41%). More women than men believed that horses express pain, jealousy, sadness, anxiety, and boredom. More participants who identified themselves as "horse owners" believed that horses are able to feel jealousy than did non-horse owners. Analysis of the open responses suggests that participants' attribution of emotional capacity to horses is in large part based on their experience with horses. Some of the behaviors described as examples of expression of pain, joy, and jealously suggest that many believed that horses are aware of their emotions. Some accounts suggested anthropomorphic projections, but others have support in scientific research. The lay understanding of horses’ emotional states and the associated contexts that elicit them may be used to educate horse owners and caretakers regarding environmental restrictions and negative human-animal interactions to which they expose horses in daily management. Our findings suggest that there is a lay knowledge base to educate those involved in the daily management of horses to change behaviors, for example, avoiding or minimizing events involving pain, fear, and boredom, and facilitating those that cause positive affective states.