A large, venerable literature demonstrates the importance of social relationships and social support for health, though much less research examines whether the benefits of social support to mothers extend to children. This paper examines the relationship between mothers' perceptions of instrumental support and children's health using longitudinal data from the U.S. Fragile Families and Child Wellbeing Study (N = 4342), a cohort of American children born in urban areas to mostly unmarried parents. Results suggest mothers' perceptions of instrumental support is positively associated with children's overall health, and this finding persists despite controlling for a host of individual-level characteristics of mothers and children (including a lagged indicator of children's health) and in fixed-effect models. Mothers' economic security and mothers' wellbeing attenuate some, but not all, of the association between perceived instrumental support and children's overall health. In addition, the link between perceived instrumental support and three specific indicators of health – asthma, overweight/obese, and number of emergency room visits – falls to statistical insignificance after accounting for individual-level characteristics, suggesting these associations result from social selection processes. Taken together, these findings suggest the beneficial health consequences of social support may extend to children across the early life course and demonstrate the need to better understand mothers' reports of children's overall health.