Objective: There is growing evidence that obesity is associated with neurological conditions like Alzheimer’s disease and reduced cognitive function in otherwise healthy adults. Poor cardiovascular fitness has been implicated as a possible mechanism for obesity related cognitive decline, though no study has examined whether body mass index (BMI) is associated with poorer cognitive function in persons with excellent fitness levels. Participants and Methods: The current study examined the relationship between BMI and cognitive function by the Immediate Post Concussion and Cognitive Test (ImPACT) in Division I collegiate athletes. Participants had an average age of 20.14 (± 1.78) years, were 31.3% female, and 53.9% football players. BMI ranged from 19.04 to 41.14 and averaged 26.72 (± 4.62). Results: Regression analyses revealed that BMI incrementally predicted performance on verbal memory (R2 change = .004, p = .260), visual memory (R2 Change = .015, p = .026) and visual motor speed (R2 Change = .003, p = .314) composite scores above and beyond age, gender, sport, and number of concussions. Follow-up partial correlation analyses revealed small but significant negative correlations between BMI and verbal memory (r = -.17), visual memory (r = -.16), and visual motor speed (r = -.12), for the entire sample. Conclusions: These results suggest that BMI is associated with cognitive function, even in a sample expected to have excellent levels of cardiovascular fitness. Further work is needed to better understand mechanisms for these associations.