Although housing is widely recognized as a crucial issue for people with severe and persistent mental illness, there is much to learn about the ongoing housing experiences of this group of people. Using secondary data, this study examined the housing histories of 65 assertive community treatment (ACT) clients from 2 years prior until up to 7 years after intake, totalling 407 addresses. We used statistical process control to assess the significance and longevity of pre- and post-ACT changes in residential tenure and independent living. We used multivariate survival analysis to explore participant and residence characteristics associated with residential stability. After 6 months in ACT, the client population showed a significant, sustained improvement in housing stability. Similarly, shortly after ACT entry, there was a marked increase in the proportion of participants living independently. At the participant level, substance abuse was the strongest predictor of residential instability; other predictors included age (30 years or younger) and sex (female). Residence characteristics also proved important; independent housing, neighbourhood income (a proxy for housing quality), and receipt of a rental subsidy were associated with significantly longer tenure, controlling for client characteristics. The timing and magnitude of the observed changes imply that ACT was effective in helping clients to achieve stable housing and to live independently. The results also underscore the importance of high-quality housing in promoting residential stability.