Background Home mathematics environment (HME) research has focused on parent–child interactions surrounding numerical activities as measured by the frequency of engaging in such activities. However, HME survey questions have been developed from limited perspectives (e.g., Early Childhood Research Quarterly, 27, 2012, 231; Journal of Social Issues, 64, 2008, 95; Early childhood mathematics education research: Learning trajectories for young children, Routledge, New York, 2009), by researchers from a small subset of countries (15; Psychological Bulletin, 147, 2020, 565), which may skew our interpretations. Aims and Sample This study broadened international representation by leveraging secondary data from the 2019 TIMSS to examine the variation of the frequency and reliability of the HME scale and its relation to children's mathematical achievement. Across 54 countries, 231,138 parents and children (Mage = 10.22 years; 51% male) participated in the larger study. Methods Parents completed a retrospective home environment survey and children were assessed on mathematics skills. Basic frequency descriptive statistics, Cronbach's alpha reliability coefficients, and Pearson's r correlation coefficients were used to assess variability across countries. Results Findings suggested that families in certain countries engaged in home mathematics activities more frequently than families in other countries; however, the HME scale demonstrated acceptable internal consistency across families in all countries (M α = .79; range = [.73, .89]). Further, the average relation between HME and mathematical achievement was r = .15 with a range between r = .02 to r = .41. Conclusion Our results indicate substantial variation across countries in the HME-mathematical achievement association. These findings underscore the importance of international representation in advancing research on the diversity of a child's home environment.