Among older adults social relationships influence mortality, but it is less clear how. We examined associations between relationship quality with spouse, child, and best friend and mortality; and whether the associations varied in the presence of chronic illnesses. Survival analyses (N = 514; 59 percent women aged ≥ 60) revealed sometimes counterintuitive main and buffering effects. Individuals who reported greater negative relationship quality with their children and friends lived longer. Buffering models suggest that relationships may exacerbate the effects of chronic illness on mortality and emphasize the importance of using a more nuanced approach when examining the effects of social relations on mortality.