Background: Estimates suggest that 20% or more of Post-9/11 Veterans have experienced at least one military-related traumatic brain injury (TBI); the majority are categorized as mild (mTBI). TBI of all levels of severity, including mTBI, can lead to chronic physical, cognitive, and emotional symptoms that, for many, interfere with daily functioning. It is also associated with comorbid diagnoses such as posttraumatic stress disorder, depression, pain, dementia, and suicidal ideation. As such, early detection and coordinated treatment are critical for preventing chronic dysfunction, disability, and early mortality among Veterans with TBI history. The VA Polytrauma/TBI System of Care (PSC), through a regional, integrated structure, serves this function by overseeing and providing screening, evaluation, education, and evidence-based treatment for those in need of TBI-related care. The PSC will care for this substantial patient population for decades to come. Since the 2014 passage of the Veterans Choice Act and, more recently, the VA MISSION Act, the VA has been outsourcing larger amounts of healthcare to non-VA providers (“Community Care”). VA Community Care may improve Veterans’ access to care; however, dual use of healthcare systems and providers can lead to poor outcomes due to fragmentation of care. Preliminary work has suggested that higher proportions of Veterans with TBI diagnoses, relative to those without TBI, are receiving VA Community Care services, and that this may be leading to the receipt of therapies that are not recommended for patients with TBI. Significance/Impact: This study will inform the development and implementation of strategies to enhance the care received by Veterans with TBI who use VA Community Care services. This work will identify gaps in the provision of evidence-based TBI care in a timely manner, as VA Community Care services continue to expand under the new MISSION Act. Our results will help ensure that Veterans with TBI receive care that is coordinated, interdisciplinary, and evidence-based, and that promotes their optimal health and functioning. Innovation: This project will develop new knowledge about Community Care utilization and outcomes among Veterans receiving care for TBI, a high-priority, clinically-complex patient population. It will be the first, to our knowledge, to measure patient-reported health and functional outcomes among Veterans who receive Community Care. Additionally, we will link to multiple VA and Department of Defense (DoD) databases to objectively account for differences in characteristics between those who do and do not use Community Care. Specific Aims: Our aims are to: (1) Describe utilization of VA Community Care (rates and types of; reliance on) among Post-9/11 Veterans with TBI; (2) Estimate associations between Veterans’ reliance on Community Care and their health and functional outcomes; and (3) Understand Veterans’ need for, perceptions of, and experiences with VA Community Care. ...