Prior research in the general population has found that social support can buffer the adverse effects of stressors on health. However, both stressors and social support may be qualitatively different for those living in urban poverty. We examined the effects of social support and poverty-specific stressors on self-rated health. We used data from the Welfare Client Longitudinal Survey (WCLS), a 5-year longitudinal study of 718 public aid recipients. We measured received social support and "net social support," defined as the difference between support received and that given to others. We used restricted cubic splines to model the stress-buffering effects of social support on self-rated health as a function of stressful life events and neighborhood disorder. Increased exposure to stressors was associated with poorer self-rated health. Evidence of stress buffering was confined to those with the heaviest exposure to stressors, and its effects decreased across increasing levels of social support. Analyses using net social support had generally more modest effects than those using received social support. Social support does not buffer the effects of stressors on health uniformly for individuals living in conditions of urban poverty. Researchers and policymakers should be cautious in overestimating the beneficial effects that social support may have on health for marginalized populations.