This study examines whether secondary schools' gender composition and levels of laddish attitudes influence the degree of ethnic prejudice among Flemish pupils. We hypothesize that in addition to pupil-level predictors of prejudice, the school's gender composition and its laddish culture play roles in pupils' attitudes toward ethnic minorities. We use multilevel analysis with data obtained in 2014-2015 from 2250 Flemish pupils in 48 secondary schools in Flanders. Both girls' and boys' ethnic prejudice is related to their laddish attitudes. Boys' levels of ethnic prejudice are associated with the gender composition and the laddish culture of their school, while girls' ethnic prejudice is more likely to be influenced by the laddish culture of the school when the proportion of male pupils in the school increases. The findings suggest that in order to reduce ethnic prejudice it might be fruitful to focus on macro-level factors, such as tackling laddish cultures at school.