This study used structural equation modeling to examine the relationship between multiple sources of social support (e.g., partner, family, and friends), optimism, and well-being among mothers of children with ASD. Social support was examined as a mediator and moderator of the optimism-maternal well-being relationship. Moreover, the role of optimism as a mediator of the social support-maternal well-being relationship was also evaluated. Results revealed that family support was associated with increased optimism that, in turn, predicted higher levels of positive maternal outcomes and lower levels of negative maternal outcomes. In addition, partner and friend support were directly associated with maternal outcomes. Implications for the development of interventions directed at increasing the quality of social support networks are discussed.