OBJECTIVE: This study compared the effectiveness of the Individual Placement and Support (IPS) model of supported employment to control vocational rehabilitation programs for improving the competitive work outcomes of people with a severe mental illness and co-occurring substance use disorder. METHODS: A secondary data analysis was conducted drawing from four randomized controlled trials comparing IPS supported employment to conventional vocational rehabilitation programs for severe mental illness, and focusing on the 106 clients with a recent (past 6 months) substance use disorder. Competitive work outcomes were tracked across an 18-month follow-up period. Analyses compared the IPS and comparison vocational programs on cumulative work over the 18 months, including attainment of work, hours and weeks worked, job tenure, wages earned, and days to first job. RESULTS: In the total study group, clients who participated in IPS had better competitive work outcomes than those who participated in a comparison program, with cumulative employment rates of 60% vs. 24%, respectively. Among clients who obtained work during the study period, those receiving IPS obtained their first job significantly more quickly and were more likely to work 20 or more hours per week at some point during the 18-month follow-up. CONCLUSIONS: The IPS model of supported employment is more effective than alternative vocational rehabilitation models at improving the competitive work outcomes of clients with a dual disorder.