Support gaps occur when an individual receives less or more of a certain type of social support than the individual desires. Existing research suggests that support gaps are associated with unwanted relationship and psychological outcomes. However, many of the outcomes associated with support gaps are also associated with received support and support availability—and it is not clear that support gaps explain anything about such outcomes beyond what is known from these longer established constructs. In samples of community members ( n = 430) and students ( n = 755), we examined associations between received support, available support, and support gaps and several positive and negative personal and relationship outcomes. Whereas received support and available support were more strongly associated with increased positive outcomes than decreased negative outcomes, support gaps were more strongly associated with increased negative outcomes than decreased positive outcomes. When all three support constructs were simultaneously included in multilevel structural equation models, they each demonstrated incremental predictive value for most of the outcomes we examined. A full understanding of the social contributions to mood and relationship outcomes requires assessment of received support, available support, and support gaps.