Research on the psychology of mountaineering has received widespread attention over many decades. Therefore, to clarify scientific findings in the area, provide future research directions, and enable the development of applied recommendations to enhance performance and safety, the purpose of this systematic mixed studies review was to identify, appraise, and synthesise research on the psychology of mountaineering. After systematically searching 10 electronic databases and undertaking manual searches up to April 2020, 69 studies published over 54 years were included in the review.Thematic synthesis was undertaken and generated 11 descriptive themes, which were captured by two analytical themes, (i) personality characteristics of mountaineers, and (ii) psychological experiences in mountaineering. The synthesis generated novel insights into connections between different research topics in the psychology-specific literature in mountaineering, thus providing a more advanced understanding of current knowledge in this area. The review highlights that considerable progress has been made in this field, but further high-quality studies are required across all facets of this literature. Future avenues for research include: group dynamics; cognitive mechanisms underlying decision-making; and coping with setbacks and traumatic events.