Research has shown that gender differences in Math performance are partially predicted by sociocultural aspects such as sexist ideologies and stereotypes. This study examined sexist ideologies as predictors of women´s achievement in standardized Math tests, and the mediation role of Math-gender stereotypes and Math self- efficacy, while controlling for abstract reasoning, among high-school girls (H.S.), and university women majoring Social Sciences and Humanities (SSH), and in Science, Technology, Engineering and Math (STEM). Among H.S. girls, data showed the expected indirect effect of Math gender stereotypes on Math achievement via Math self-efficacy. Among university students, model adjustment was less optimal. An unexpected positive relationship between hostile sexism and Math performance in STEM fields emerged. Out data suggest several mechanisms by which ideologies and gender stereotypes affect women´s Math performance.