This study examines the relations among parental beliefs and practices about mathematics, children's beliefs about mathematics, participants' gender, and family socioeconomic status (SES). The study was conducted in Chile, a country with significant gender gaps in standardized test results in mathematics, with boys receiving significantly higher scores than girls. One hundred eighty Chilean kindergarteners (M[subscript age] = 5.6 years) of low and high SES completed both implicit and explicit measures of their beliefs about mathematics. Children's mothers and fathers also completed adult versions of these tests, as well as measures of home numeracy practices. This combination of child and parental assessments (both mother and father), including both implicit and explicit measures, provided a wider range of measures than in previous studies. On implicit measures of math-gender stereotypes, boys showed the math = boy stereotype significantly more strongly than girls did. Both fathers and mothers showed this stereotype on both implicit and explicit measures. Fathers also linked me = math (math self-concept) more strongly than mothers on both implicit and explicit measures. Kindergarten girls' implicit math self-concept was explained by a combination of parents' math self-concepts and SES. Taken together, these results show that by 5 years of age children are already developing beliefs about "who does math" in their culture, and that parental beliefs and practices are significantly linked to children's stereotypes and self-concepts about mathematics before they enter formal schooling.