Openness to experience has been shown to have a positive impact on mental health in the general population, but there is a dearth of information both about why this is the case and on LGB populations in this area. The present article explores the relationship between openness to experience, LGB identity development, and mental health. The results revealed a full mediation model, where the positive impact of openness to experience on mental health is fully mediated by positive LGB identity development. Limitations and implications are discussed.