Community-based models of providing mental health services are widely considered effective ways of serving individuals diagnosed with mental illness, but more comprehensive literature on these models in low- and middle-income countries is needed. This study is a systematic review of the effects of community-based models on health outcomes of adults with depression, schizophrenia, panic disorder, or bipolar disorders in middle- and low-income countries. PubMed, PsycINFO, and Cochrane Reviews were searched, returning 500 articles. The seventeen interventions included in this review in 14 countries show us that community-based mental health services can provide improvements in mental health outcomes, and the limited cost analyses suggest cost savings associated with community models of care. These findings are in line with much of the research on higher income countries. In addition, the studies also point to the gaps in the literature on costs, rural areas, bipolar disorders, and panic disorders, and note the need for further reviews of interventions targeting additional diseases, children, and adolescents as well as studies published in languages other than English. This review of the literature serves as a stepping stone for further research in community-based mental health services in low- and middle-income countries. The works reviewed here provide a base of knowledge that will assist us in taking the important next steps in program implementation and evaluation.