Nativity differences in birth outcomes in the United States are well documented, with more favorable outcomes among children of foreign-born parents than those of native-born parents. Using longitudinal data on mothers from the U.S. Fragile Families Study (N~4,000) and the United Kingdom Millennium Cohort Study (N~15,000), we provide a comparative and longitudinal perspective on nativity differences in mothers' health behaviors. First, we ask whether healthier behaviors observed among Hispanic immigrants in the United States extend to foreign-born mothers in the United Kingdom., including South Asian, black African and Caribbean, and East Asian immigrants. Second, we consider the persistence of differences throughout early childhood. The findings demonstrate healthier behaviors among foreign-born mothers in both the United States and the United Kingdom, including both socioeconomically disadvantaged and advantaged mothers. These differences are stable over early childhood, suggesting a “universality” of healthier behaviors among foreign-born mothers—spanning racial/ethnic and socioeconomic groups, time, and two different policy contexts.