Although growing evidence suggests a link between children's math skills and their ability to estimate numerical quantities using the approximate number system (ANS), little is known about the sources underlying individual differences in ANS acuity and their relation with specific mathematical skills. To examine the role of intergenerational transmission of these abilities from parents to children, the current study assessed the ANS acuities and math abilities of 54 children (5–8 years old) and their parents, as well as parents' expectations about children's math skills. Children's ANS acuity positively correlated with their parents' ANS acuity, and children's math abilities were predicted by unique combinations of parents' ANS acuity and math ability depending on the specific math skill in question. These findings provide the first evidence of intergenerational transmission of an unlearned, non‐verbal numerical competence and are an important step toward understanding the multifaceted parental influences on children's math abilities. Although growing evidence suggests a link between children's math skills and their ability to estimate numerical quantities using the approximate number system (ANS), little is known about the sources underlying individual differences in ANS acuity and their relation with specific mathematical skills. Here we find that parents' ANS acuity correlates with their children's ANS acuity, and parent's math ability predicts their children's math ability across a number of math measures. These findings provide the first evidence of intergenerational transmission of an unlearned, non‐verbal numerical competence and are an important step toward understanding the multifaceted parental influences on children's math abilities.