Objective: The objective of this study was to determine if there was an effect of sleep on self-reported symptom presentation and/or computerized neuropsychological test scores in a standard concussion management program. Sleep has long been known to affect cognitive performance, although some research has shown less effect on standardized neuropsychological tests. Symptom presentation is a standard element of concussion assessment and is frequently the primary element of concussion assessment. Current protocols require baseline assessment against which post-concussion assessment results are compared. Thus, the validity and reliability of baseline findings are of critical importance. Participants and Methods: Data was analyzed from 2,002 high school athletes (1,159 male, 843 female) who were administered a computerized neuropsychological screening test (ImPACT) and health history questionnaire. Number of previous concussions, learning disability status and age were shown to account for significant variance in test scores and symptoms, and were used as covariates in a regression equation. Sleep related symptoms were removed from the symptom scale. Results: Sleep the night before had no significant effects on test scores, but the effect on symptoms was significant. Hours of sleep the night before testing was shown to be related to self-reported symptoms, after controlling for covariates (males: β = -.438, p =.002; females: β= .955, p <.001). Conclusions: Lowered amounts of sleep the night before testing was related to an increase in symptom totals, which could reduce the difference between baseline and post-test scores. Smaller differences in symptom totals may make an athlete appear less symptomatic (relative to baseline) and thus interpreted as non-concussed from a symptom point of view.