OBJECTIVE: In the context of increased uptake of flexible assertive community treatment (FACT)-despite a dearth of evidence on its outcomes-the authors aimed to compare the effectiveness of FACT with that of assertive community treatment (ACT) or intensive case management (ICM) for community-dwelling people experiencing serious mental illness. METHODS: This quasi-experimental study, using propensity score matching to minimize confounding factors, examined outcomes of acute psychiatric service use among individuals who received FACT (vs. ACT or ICM) at a large Canadian mental health hospital. Data from a period of transition to FACT and an implementation period were analyzed. RESULTS: The matched cohort consisted of 237 FACT and 237 ACT or ICM service users. During the transition period, no significant differences between the two groups were observed in emergency department (ED) visits, hospital admissions, or inpatient days. During the period of full FACT implementation, the FACT group had a significant increase in ED visits, compared with the group that received ACT or ICM (incidence rate ratio=1.65, 95% CI=1.02-2.67), but no significant differences were observed between the two groups in the rate of hospital admissions or inpatient days. CONCLUSIONS: To the authors' knowledge, this study is the first of its kind in Canada. Its findings suggest generally comparable outcomes of FACT (vs. ACT or ICM) in acute mental health services use. Although the rate of ED service use increased in the FACT group after implementation, inpatient service use did not increase. The higher rate of ED service use in the FACT group warrants further study.