Background Despite large‐scale dissemination and implementation efforts of evidence‐based psychotherapy to veterans from Operation Enduring/Iraqi Freedom (OEF/OIF), little is known regarding the factors that contribute to the successful completion of these treatments in this high‐risk population. The present study investigated predictors of treatment completion during a standardized exposure‐based psychotherapy for PTSD. Methods Ninety‐two OEF/OIF combat veterans enrolled in a randomized controlled trial for an eight session exposure‐based psychotherapy for PTSD. All participants completed structured clinical interviews and several background and symptom questionnaires. Of the initial 92 participants, 28% of the sample (n = 26) discontinued treatment prior to completion of the trial. Results Predictors of discontinuation of treatment were assessed with a hierarchical logistic regression. Disability status was positively associated with treatment discontinuation, and postdeployment social support was negatively associated with discontinuation. In contrast to previous findings, other factors, such as age and PTSD symptomatology, were not identified as significant predictors. Conclusions The present study suggested that disability status at the start of treatment increases the risk for treatment discontinuation whereas increased social support buffers against discontinuation. Together, these findings highlight the importance of increased assessment and early intervention when these factors are present to potentially reduce treatment discontinuation and improve treatment outcomes in OEF/OIF veterans with PTSD.