Threats to masculinity can trigger compensatory mechanisms such as risk-taking, aggression, or disparagement of gender atypical others. In Study 1 (N = 76) we tested whether threat to men's agentic self (information about the level of testosterone) influences men's (a) attitudes toward parental duties, and (b) their support for gender equality. Polish men (but not women) whose gender identity was threatened manifested more traditional attitudes toward parental duties, were more willing to endorse stereotypical gender roles, and showed less support for gender equality and less willingness to support collective egalitarian actions. In Study 2 (N = 313) we found that agency is related to gender system justification in men, suggesting a potential mediator of the effects related to compensatory mechanisms evoked by a gender identity threat among men. This was confirmed in Study 3 (N = 131), where participants read a short scientific text either (a) emphasizing the existence of stereotypical gender differences in terms of agency and communality, or (b) claiming that there are no such differences. Results indicated that in the "no differences" condition, men (but not women) showed lower acceptance of gender inequality and a greater willingness to engage in domestic activities. This effect was mediated by participants' self-perceived agency.