National as well as international standardized assessments reveal that Chile has a large gender gap in math achievement that favors male students. Some theories propose that at least part of this gap can be explained by the effects of gender stereotypes that refer to abilities in math. In the present study, we examine the implicit and explicit gender stereotypes related to math of kindergarten children, their mothers, fathers and teachers in Santiago, Chile. The participants were 180 kindergarteners from mid-low and high SES (87 girls and 93 boys, from 19 classrooms), their parents and classroom teachers, from the urban area of Santiago, Chile. Participants were assessed on explicit and implicit gender stereotypes on math ability. Results show that, on average, both adults and children hold a stereotype that associates math to the male gender. In the case of children, the results of the implicit assessments reveal that all of the boys and mid-low-SES girls relate math to the male gender, while high-SES girls do not associate math to any gender. These findings suggest that math and gender stereotypes could help explain part of the math gender gap present in Chile, and thus suggest opportunities for early interventions and public policies that seek to offer children equal learning opportunities, particularly for girls and mothers from mid-low SES, who most intensely present this stereotype.