This paper uses recent longitudinal data about a cohort of young children born in the United States to mostly unmarried parents to examine the association between increasingly-complex patterns of family instability and physical health in early childhood. The analyses assess whether, and how, the association between family instability and child health varies across a number of family types. We consider several measures of children's health at age five (overweight/obesity, asthma diagnosis and overall health) and examine to what extent the association between family instability and child health varies across outcomes and depends on the number and timing of any familial transitions. We also explore a number of potential mechanisms through which family instability may affect child health. The results suggest that familial instability is related to worse child health, particularly among children born to coresident (married or cohabiting) biological parents and for children who experience high levels of residential instability.