Within cultures, people develop a shared gender belief system that includes the content of gender stereotypes, masculinity and femininity, and attitudes toward people who deviate from traditional gender roles (i.e., sexism). In the present work, we first explored gender belief systems in Poland-a country lower in gender equality-and in Norway-a country higher in gender equality. Results from 458 participants showed that young Poles more strongly endorsed stereotypes about men than Norwegians. They prescribed more agency and less communality to men than did young Norwegians. In addition, Poles reported more hostile sexism and stronger endorsement of precarious manhood than young Norwegians. Then, based on previous research-mostly conducted in the United States-that has shown that manhood is perceived to be precarious and men experience negative emotions and concern about others' perceptions of them when their masculinity is threatened, we conducted a second study with 443 men and women from Poland and Norway. In this study, participants received false feedback about their level of masculinity versus femininity based on a "gender knowledge test." Results showed that Polish men-but not women-who received feedback that they had feminine gender knowledge (i.e., masculinity threat condition) reported more concerns about others' perception of them and more negative emotions than Norwegian men and women. The importance of cross-national comparisons in psychological research and the consequences of cultural differences in gender belief systems and culture-specific responses to masculinity threat are discussed.