In the fields of education, sociology, and economics, there is a long-standing connection between socioeconomic status (SES) and school outcomes in a wide variety of cultural settings, but these studies have yet to examine the possible mediating effects of domain-general cognitive factors such as executive functions (EFs). Addressing this gap and building on evidence for links between EFs and numeracy, the current cross-cultural study used a large sample (N = 835) of 9- to 16-year-old children from Hong Kong and the United Kingdom to examine the independence and interplay of SES and EFs as predictors of numeracy skills. Our analyses yielded three key findings, namely that (a) EFs consistently predicted numeracy skills across sites and genders, (b) associations between SES and EFs differed by site and gender, and (c) associations between numeracy skills and SES/EFs differed by site and gender. Together with previous findings, our results suggest culture-specific associations among SES, EFs, and numeracy, indicating that cultural insights may enable impactful shifts in public policy to narrow the achievement gap between children from affluent and disadvantaged families.