Objective: To investigate the pre- to posttreatment changes in both posttraumatic stress disorder (PTSD) and persistent postconcussive symptoms (PPCSs). Setting and Participants: We studied 257 active-duty patients with a history of mild traumatic brain injury (mTBI) who completed multidisciplinary outpatient treatment at Brooke Army Medical Center TBI Clinic from 2008 to 2013. This treatment program included cognitive rehabilitation; vestibular interventions; headache management; and integrated behavioral healthcare to address co-occurring psychiatric conditions such as PTSD, depression, and sleep disturbance. Design: A 1-group; preexperimental, pre- to posttreatment study. Main Measures: The Neurobehavioral Symptom Inventory (NSI) was used to assess PPCSs, and the PTSD Checklist Military Version (PCL-M) was used to asses PTSD symptoms. Results: Global PPCS resolution (mean NSI: 35.0 pre vs 23.8 post; P .0001; d = 0.72) and PTSD symptom resolution (mean PCL-M: 43.2 pre vs 37.7 post; P .0001; d = 0.34) were statistically significant. Compared with those with only mTBI, patients with mTBI and PTSD reported greater global PPCS impairment both pretreatment (mean NSI: 48.7 vs 27.9; P .0001) and posttreatment (mean NSI: 36.2 vs 17.4; P .0001). After adjusting for pretreatment NSI scores, patients with comorbid PTSD reported poorer PPCS resolution than those with mTBI alone (mean NSI: 27.9 pre vs 21.7 post; P = .0009). Conclusion: We found a reduction in both self-reported PPCSs and PTSD symptoms; however, future studies are needed to identify specific components of care associated with symptom reduction.