The challenge of providing effective treatment services for the growing population of HIV-positive individuals who are also dually diagnosed with substance use and mental disorders has only recently been recognized as an important public health concern affecting both HIV treatment and prevention. This article describes a treatment model that was created for a study of integrated treatment for HIV-positive individuals with substance use and mental disorders. The treatment model was based on the transtheoretical model of behavior change as well as evidence-based practices that are widely used in the treatment of individuals dually diagnosed with substance use and mental disorders. The model involved collaboration between medical and behavioral health care professionals and emphasized the importance of goal reinforcement across disciplines. Furthermore, it included the development and enhancement of client motivation to modify medical and behavioral health-risk behaviors using individual readiness for change and offered comprehensive care addressing a continuum of client needs that may influence treatment outcomes. Treatment modalities included individual therapy, group therapy, and psychiatric medication management. This treatment intervention was associated with positive outcomes in the integrated treatment study and can be adapted for use in a variety of psychiatric or medical treatment settings.