Abstract: Massed (≥ 3 times a week) delivery of psychotherapy for posttraumatic stress disorder (PTSD) has emerged as an alternative to traditional "spaced" (weekly/bi-weekly) delivery. Massed delivery has been shown to be non-inferior to spaced delivery, with higher rates of treatment completion. This pilot project evaluated the effectiveness of massed delivery in Department of Veterans Affairs (VA) PTSD Residential Rehabilitation Treatment Programs (RRTPs). A massed treatment program called Models of Accelerated Service Delivery (MASD) was piloted in six RRTPs. Data from Veterans who received either MASD or non-MASD delivery at a pilot site between 10/2022–09/2023 were included in this evaluation (n = 466). Veterans received PTSD symptom assessment at admission, discharge, and 1-year post-discharge. A hierarchical linear modeling (HLM) approach was used to evaluate trajectories of PTSD symptom change between delivery approaches. Veterans who received MASD delivery of PTSD psychotherapy had significantly shorter lengths of stay as well as higher rates of treatment completion. Veterans participating in RRTP treatment experienced symptom attenuation, with no observed differences in the trajectory of symptom change between delivery approaches. This pilot project provides preliminary support for the MASD program in residential treatment. Further research is needed to understand how treatment decisions are made by clinicians and Veterans.