BACKGROUND: Supported employment has long been recognized as one of the most effective services for individuals with the most significant disabilities in achieving competitive integrated employment (CIE) outcomes. OBJECTIVE: This study examined the effect of supported employment interventions on the employment outcomes of transition-age youth and young adults with intellectual disabilities served by state vocational rehabilitation agencies using a propensity score matching (PSM) approach. METHODS: We conducted a non-experimental causal comparative study with PSM to create a treatment (n = 2162) and a comparison group (n = 2191) using the Rehabilitation Services Administration Case Service Report database (Program Year 2018). Chi-square and t-test were used to analyze the differences between the treatment and control groups on employment outcomes, hourly wage and hours worked per week. RESULTS: Results demonstrated that transition-age youth and young adults with intellectual disabilities who received supported employment were more likely to achieve CIE, earn higher wages, and work longer hours weekly than were the control group. CONCLUSION: These findings suggest that supported employment is an effective service for enhancing the vocational rehabilitation outcomes of transition-age youth and young adults with intellectual disabilities and provides valuable information for policy makers, health care providers, rehabilitation counselors, and educators.