Approximately half of patients with schizophrenia have a lifetime diagnosis of substance abuse disorders. These dual diagnosis patients are more likely to have poorer outcomes, including more severe psychiatric symptoms with increased hospitalizations, higher utilization of services and frequent homelessness. Assessment and treatment of dually diagnosed patients has evolved over the last twenty years. To date, the strongest evidence for effective management of dual diagnosis patients has been utilization of integrated treatment services, which combines both mental health and substance abuse treatments concurrently. Strategies commonly used include a combination of pharmacological treatment, intensive case management, motivational interviewing, individual and group psychotherapy, and family participation. This chapter summarizes the treatment options available for this population.