Sexist beliefs from 3193 secondary school students (50.4% men) of Castilla-La Mancha (Spain) are analyzed in the light of ambivalent sexism theory. This research aims to study the relationship between school bullying and adolescent’s sexist beliefs, especially among male youths. The Ambivalent Sexism Inventory and the Instrument to assess the incidence of involvement in bully/victim interactions at school were used to gather data. The results show that sexism has significant effects on bullying behaviors. The results are discussed and taken into consideration in the design of prevention interventions.