There is a global mental health crisis: mental illness is underrecognized, underdiagnosed, and undertreated with adverse effects on mental, physical, and social health. In the United States, there is an insufficient number of traditional psychiatric and psychological resources to provide the mental health care needed to solve this crisis. Community-based interventions could be an important adjunct to traditional mental health care. An evaluation of peer-reviewed articles was performed describing community-based interventions and identified 3 approaches with some evidence of effectiveness: (1) interventions that enhance community mental health literacy to improve recognition of early signs of mental illness for early engagement and provide community, family, and peer support; (2) community clinics providing social, medical, and mental health care and support to transition-age youth (15-25 years); and (3) social networking activities to enhance interactions among elders suffering from social isolation and loneliness. Multisector, multidisciplinary, and multicomponent interventions involving health care providers and community-based organizations had the best evidence of effectiveness and should target transition-age youth and elders.