This study examined whether an adapted Assertive Community Treatment (ACT) intervention improved substance use, mental health, physical health, legal, employment, and housing outcomes for a U.S. sample of homeless men with a substance use disorder or a dual-diagnosis of substance use and mental health disorders and whether this intervention was equally effective for a subgroup of minority men. Data were collected from 103 participants who received treatment services for up to 12 months. The intervention significantly reduced recent substance use, the severity of problems and the number of hospitalizations related to substance use. The intervention also improved mental health problem severity and legal outcomes. The proportion of men living in stable housing increased at 12-month follow-up, whereas the severity of employment problems increased over time yet decreased for those who more fully utilized the services provided by the program. In general, the intervention was equally effective for minority and non-minority men.