The frequent co-occurrence of substance abuse disorders along with psychiatric disorders creates a number of complexities and needs in terms of long-term treatment for individuals. 12-step groups might provide unique mechanisms by which dually-diagnosed individuals can maintain their abstinence and improve their psychological functioning. This paper reviews the literature on outpatient community 12-step participation among dually-diagnosed individuals, and also focuses on individual factors that may interact with treatment: homelessness, legal status, and ethnicity. A total of 59 articles was included in the review, with an emphasis on these individual factors and findings regarding mechanisms of action. Overall, findings from the studies reviewed suggest a general benefit of 12-step participation across these individual factors and some potential for dual-focus 12-step programs for dually-diagnosed individuals via social support and self-efficacy. However, methodological limitations and lack of research in the area of ethnicity limited some of the conclusions that can be made. Suggestions for further research are discussed.