Men may have evolved psychological mechanisms that motivate mate retention behaviors to prevent their partners from being sexually unfaithful or defecting from the relationship because these events are likely to have inflicted reproductive costs on males over human evolutionary history. In the current research, 235 women provided information about their own and their long-term partners’ mate value relative to alternatives, as well as information about their partners’ mate retention behaviors. Men’s mate value is a better predictor of men’s mate retention behaviors than is women’s mate value. Specifically, men of higher mate value perform more benefit-provisioning and fewer cost-inflicting mate retention behaviors than men of lower mate value. The discussion notes limitations and highlights directions for future research.