Objective: To examine whether cognitive reserve (CR) attenuates the initial impact of traumatic brain injury (TBI) on cognitive performance (neural reserve) and results in faster cognitive recovery rates in the first year postinjury (neural compensation), and whether the advantage of CR differs on the basis of the severity of TBI. Setting: Inpatient/outpatient clinics at an academic medical center. Participants: Adults with mild TBI (mTBI; n = 28), complicated mild TBI (cmTBI; n = 24), and moderate to severe TBI (msevTBI; n = 57), and demographically matched controls (n = 66). Design: Retrospective, longitudinal cohort assessed at 1, 6, and 12 months postinjury. Main Measures: Outcomes were 3 cognitive domains: processing speed/executive function, verbal fluency, and memory. Premorbid IQ, estimated with the Wechsler Test of Adult Reading, served as CR proxy. Results: Higher premorbid IQ was associated with better performance on cognitive domains at 1 month postinjury, and the effect of IQ was similarly beneficial for all groups. Cognitive recovery rate was moderated only by TBI severity; those with more severe TBI had faster recovery in the first year. Conclusion: Results support only the neural reserve theory of CR within a TBI population and indicate that CR is neuroprotective, regardless of the degree of TBI. Higher premorbid CR does not allow for more rapid adaptation and recovery from injury.