Masculine self-concept refers to a man's psychological sense of being male. In this study, we used the Semantic Misattribution Procedure to assess men's implicit masculine self-concept. As expected, implicit masculine self-concept was not associated with social desirability, but was positively associated with several gender-relevant outcomes, including conformity to masculine norms, endorsement of traditional masculinity ideology, hostile sexism, and benevolent sexism. We also found support for a mediation model in which explicit masculine self-concept mediated the impact of implicit masculine self-concept on these outcomes. These results provide evidence for the importance of implicit masculine self-concept when exploring gender-relevant outcomes.