Horses are depended on as work animals by humans and are used in leisure and sport across the world, but the extent to which humans can recognise pain in horse faces is not known, which could impact their welfare. There are also significant gaps in our understanding of which psychological traits influence recognition of human facial expressions of pain. To address this, one hundred participants, with either some (N = 30) or no prior horse care experience (N = 70), rated thirty human and thirty horse faces for pain, arousal and valence and completed trait measures of empathy and social anxiety. Ten equine behaviour professionals also rated the horse faces as a baseline for assessing accuracy. Overall, accuracy of pain recognition was higher for human faces, but participants with horse experience were more accurate at pain recognition in horse faces, than those without, and years of horse experience predicted horse pain recognition accuracy. Social anxiety traits predicted accuracy of pain recognition in human but not horse faces, while also predicting subjective ratings of pain in horse but not human faces. Empathy and its cognitive and emotional components were not related to pain recognition accuracy or ratings of horse or human faces. Relationships between trait measures and arousal and valence ratings for both species are reported. This study is the first to report the human ability to read pain in horse faces and the factors which influence this and extends current knowledge on face processing in social anxiety.