Objective: Supported housing programs have been successful in helping homeless adults obtain housing. This study examined whether improvements in social integration occur after clients obtain supported housing. Methods: Measures of social integration were examined for 550 chronically homeless adults with mental illness who participated in the 11-site Collaborative Initiative to Help End Chronic Homelessness. Social integration was conceptualized as a multidimensional construct of variables in six domains: housing, work, social support, community participation, civic activity, and religious faith. Changes in baseline measures related to the six domains and their interrelationships were examined at six and 12 months after entry into the supported housing program. Results: Chronically homeless adults showed substantial improvements in housing but remained socially isolated and showed limited improvement in other domains of social integration, which were only weakly correlated with one another. Conclusions: More attention is needed to develop rehabilitation interventions in supported housing programs to improve social integration of chronically homeless adults. Because improvements in some domains of social integration were only weakly related, it may be necessary to intervene in multiple domains simultaneously.