Early childhood is a critical period in the life course, setting the foundation for future life. Early life contexts—neighborhoods and families—influence developmental outcomes, especially when children are exposed to economic and social disadvantage. Residential mobility, frequent among families with pre-school children, may reduce or increase exposure to adverse surroundings. We examine children’s cognitive and behavioral outcomes at age five, in relation to neighborhood composition, family circumstances and residential moves, using two longitudinal micro datasets: an urban subsample of the UK Millennium Cohort Study (N up to 7967), and the Fragile Families and Child Wellbeing Study in the US (N up to 1820). Each is linked to an index of neighborhood advantage, created to make UK/US comparisons, based on census and administrative information. A series of estimates indicate a strong association, in both countries, between cognitive scores and neighborhood advantage, attenuated but not eliminated by family circumstances. Children’s behavior problems, on the other hand, show less association with neighborhood advantage. There are minor and mixed differences by residential mobility particularly when neighborhood disadvantage changes. Notwithstanding the primacy of the family in predicting preschool development, the findings support the notion of neighborhood as potentially advantageous at least in relation to cognitive outcomes.