This report evaluates the Denver Supportive Housing Social Impact Bond Initiative (Denver SIB), which sought to increase housing stability and reduce jail stays among chronically homeless persons with prior frequent involvement with the criminal justice and emergency health systems. Under Denver SIB, supportive housing was provided through a Housing First approach (which had no preconditions or requirements for participants) and a modified Assertive Community Treatment (ACT) model. ACT is a multidisciplinary team-based approach to deliver supportive services, such as case management, crisis intervention, substance use counseling, mental health treatment, peer support, skills building, and connection to primary care.