Mild traumatic brain (TBI) injuries are difficult to diagnose with standard imaging techniques, and currently lack adequate biomarkers for disease diagnosis and monitoring. The heterogeneity of TBI etiology challenges efforts to discover sufficiently robust and accurate molecular biomarkers of TBI endophenotypes. While much progress in this area has been made using protein-based biomarkers of neuronal and astrocyte cell damage for grading injury severity, biomarkers indicating the activation of specific underlying pathologic processes are needed to evaluate and suggest personalized interventions. The work of this thesis aims to investigate the diagnostic potential of brain derived extracellular vesicles (EVs), a diverse class of lipid enclosed nanoparticles shed from virtually all brain cell types with molecular cargo reflecting the state of their origin cells. We utilize an emerging strategy known as Track Etched NanoPOre (TENPO) to enrich for EVs based on their expression of Glutamate Ionotropic AMPA Receptor Subunit 2 (GluR2) and predominantly originating from neurons, and those expressing GLutamate ASpartate Transporter (GLAST) and predominantly originating from astrocytes. We combine this technology with tools of molecular biology – namely ultrasensitive protein detection and next-generation sequencing of microRNA – to analyze the molecular cargo of these EV populations. We demonstrate using plasma samples obtained from mild TBI patients and healthy volunteers that TBI elicits alterations in the distribution and expression of EV molecular cargo and illustrate that different EV populations and plasma possess independent, yet potentially complimentary information on the state of the injured brain. We also show that this independence of molecular information across EV populations and in plasma persists over time in a swine model of rotational acceleration based TBI. Together, the work of this thesis suggests brain derived EV populations may be well suited to provide therapeutically meaningful information about an individual’s TBI currently inaccessible with traditionally studied protein biomarkers or brain imaging modalities.