This research examined the influence of a romantic partner's success or failure on one's own implicit and explicit self-esteem. In Experiment 1, men had lower implicit self-esteem when their partner did well at a "social intelligence" task than when their partner did poorly. Women's implicit self-esteem was unaffected by partner performance. Experiments 2 and 3 showed that Dutch men's implicit self-esteem was negatively affected by their romantic partner's success. In Experiment 4, we replicated Experiments 1-3 in both the academic and social domains, and in Experiment 5, we demonstrated that men's implicit self-esteem is negatively influenced by thinking about a romantic partner's success both when the success is relative and when it is not. In sum, men's implicit self-esteem is lower when a partner succeeds than when a partner fails, whereas women's implicit self-esteem is not. These gender differences have important implications for understanding social comparison in romantic relationships.