The current project examined the impact of differential motivation on baseline versus post-mild traumatic brain injury (MTBI) neuropsychological measures in athletes. Collegiate athletes were administered a neuropsychological battery prior to and post-MTBI. High Motivation at Baseline (HMB) and Suspect Motivation at Baseline (SMB) groups were established for each measure based on whether baseline performance fell +/- one or more standard deviations from the mean of the given measure. Greater improvement was expected in the SMB group than the HMB group given hypothesized differences in baseline motivation. In repeated measures analysis of covariance (ANCOVA) that removed achievement performance, the SMB groups demonstrated greater improvement than the HMB groups for the Trail Making Test A & B (TMT-A & B), Digit Span, and Stroop-Color Word (Stroop-CW) tests. Also, the percentage of participants who improved according to reliable change indices was greater for the SMB groups on the TMT-A & B, Stroop-CW, and the Vigil. These findings are likely due to lower motivation in the SMB group for each test. However, results also suggest that some tests may be relatively unaffected by motivation. These data may have clinical implications and point to the need for better methods of identifying athletes with suspect motivation at baseline.