Homeless individuals with co-occurring mental and substance abuse disorders are at high risk for victimization and violence, frequently cycle between the streets, jails, and emergency rooms, and are difficult to effectively treat because of their multifaceted problems. This study evaluates Project HOPE, an intensive, integrated outreach program for this population. We found that Project HOPE effectively enrolled a highly at-risk, symptomatic group of 69 clients in treatment. However, the majority (62%) of these clients discontinued treatment in less than three months. Those who completed Project HOPE showed remarkable improvement across several domains, including more stable housing, fewer psychiatric and substance abuse problems, and better relationships. In this first study of treatment-related changes in violence and victimization for this population, we found that victimization rates decreased from 67% to 16% and violence rates decreased from 46% to 20% with treatment. Implications for developing programs that better retain clients while effectively improving their symptoms, safety, and functioning are discussed.