Building on a conceptual model of the transition to elementary school, this study explored the role of health in the early cognitive achievement of children from various racial/ethnic minority and immigrant families by applying multilevel modeling to data from a nationally representative sample of American kindergarteners. Whites tended to have the best physical health before transitioning to first grade. Children from immigrant Latino/a and Asian families had the worst physical health but the best mental health. Compared to white children from native families, these health differentials partially explained the lower math achievement and achievement growth of black children (whether from native or immigrant families) in first grade as well as the lower math achievement of children from Latino/a immigrant families and the lower achievement growth of children from Asian immigrant families during this period. (Contains 4 tables and 1 figure.)