Post-traumatic stress disorder (PTSD) leads to significant disability, unemployment, and substantial healthcare costs. The cost-effectiveness of vocational rehabilitation (VR) interventions is important to consider when determining which services to offer. This study assesses the cost-effectiveness and return on investment of Individual Placement and Support (IPS) compared to transitional work (TW) programs. Employment outcomes from a multisite randomized trial comparing IPS to TW in military veterans with PTSD (n = 541) were linked to Veterans Health Administration (VHA) archival medical record databases to examine the comparative cost-effectiveness and return on investment. Effectiveness was defined as hours worked and income earned in competitive jobs. Costs for VR, mental health, and medical care and income earned from competitive sources were annualized and adjusted to 2019 US dollars. The annualized mean cost per person of outpatient (including vocational services) were $3970 higher for IPS compared to TW ($23,245 vs. $19,276, respectively; P = 0.004). When TW income was included in costs, mean grand total costs per person per year were similar between groups ($29,828 IPS vs. $26,772 TW; P = 0.17). The incremental cost-effectiveness analysis showed that while IPS is more costly, it is also more effective. The return on investment (excluding TW income) was 32.9% for IPS ($9762 mean income/$29,691 mean total costs) and 29.6% for TW ($7326 mean income/$24,781 mean total costs). IPS significantly improves employment outcomes for individuals with PTSD with negligible increase in healthcare costs and yields very good return on investment compared to non-IPS VR services.