This study examined the association between low-income mothers' perceived social support and the prevalence of their children's medically treated accidents and injuries. Data were drawn from the National Evaluation of Welfare-to-Work Strategies (NEWWS), an experimental evaluation of 11 welfare-to-work programs in seven U.S. cities. In regression models, maternal social support was significantly associated with the likelihood that children experienced an accident or injury between the ages of 8 and 10 such that children of mothers with very limited support were at the highest risk. This association was robust to the inclusion of a wide range of controls, including a prior measure of accident and injury occurrence. A primary finding was that only children whose mothers had the lowest levels of social support, characterized here as socially isolated, suffered significantly higher rates of injury. This suggests that social isolation presents a meaningful threat to child safety and may play an important role in the etiology of child injury among low-income families.