Objective: The association of dispositional optimism with health-related factors has been well established in several clinical populations, but little is known about the role of optimism in recovery after traumatic brain injury (TBI). Given the high prevalence of cognitive complaints after TBI, the present study examined the association between optimism and cognitive functioning after TBI. Methods: 171 individuals with complicated mild, moderate or severe TBI completed a series of questionnaires via structured interview and self-report, including a self-report assessment of dispositional optimism, the revised Life Orientation Test (LOT-R), and an objective assessment of cognition, the Brief Test of Adult Cognition by Telephone (BTACT). Multiple hierarchical regression analysis was conducted to examine the relationships between optimism and cognitive functioning. Results: Dispositional optimism was significantly and positively associated with post-TBI cognitive functioning after controlling for the effects of age, race, injury severity, health status, and positive and negative affect. Conclusion: Dispositional optimism may promote higher levels of cognitive functioning in people who sustained a TBI. Research is warranted to examine whether interventions that promote optimism in clinical and social encounters can enhance cognitive recovery in individuals with TBI.