Relatively high levels of depression are observed during the transition to adulthood. Hence, it is important to identify the factors that can reduce the incidence of depression at this time. Social capital is theorised to protect against depression by providing greater access to support and psychological resources. Social capital incorporates both interpersonal relationships and broader community-level factors. However, most research has focused on the influence of relationships with parents and peers in the development of depression in young people, with little attention given to the role of broader social capital factors relating to perceptions of and engagement with the wider community. Drawing on longitudinal data from the Australian Temperament Project (ATP), this article examines the effects of close interpersonal relationships (with parents and peers) and broader, community-level aspects of social capital (trust and civic engagement) on depression during the transition to adulthood. Using hierarchical multiple regression, alienation from peers was found to predict higher depression, whereas good communication with peers was associated with a reduction of depressive symptoms. After controlling for the effects of close interpersonal relationships, trust in authorities and organisations made a significant contribution to the prediction of lower depression. Implications for intervention are discussed.