This article uses data from the Fragile Families and Child Wellbeing study to explore the characteristics and determinants of homelessness among families with children. These unique data permit the examination of a large set of individual‐, household‐, and city‐level risk factors that may influence homelessness. Results suggest that homelessness is strongly linked to informal and institutional social support. It is only modestly associated with local housing and labor market conditions. These results suggest that the greatest potential for reducing family homelessness lies in interventions, such as low‐income housing assistance, that are designed to strengthen informal and institutional social support among low‐income mothers. Policies designed to alter local housing and labor market conditions are unlikely to reduce substantially the risk of this pressing social problem.