OBJECTIVES: To evaluate the efficacy of cognitive and physical rest for the treatment of concussion. STUDY DESIGN: High school and collegiate athletes (N = 49) underwent post-concussion evaluations between April 2010 and September 2011 and were prescribed at least 1 week of cognitive and physical rest. Participants were assigned to groups on the basis of the time elapsed between sustaining a concussion and the onset of rest (1-7 days, 8-30 days, 31+ days). Main outcome measures included Concussion Symptom Scale ratings and scores on the 4 composite indices of the Immediate Post-Concussion Assessment and Cognitive Testing measure, both before and following rest. Mixed-factorial design ANOVA were used to compare changes on the dependent measures within and between groups. RESULTS: Participants showed significantly improved performance on Immediate Post-Concussion Assessment and Cognitive Testing and decreased symptom reporting following prescribed cognitive and physical rest (P < .001), regardless of the time between concussion and onset of rest (P = .44). CONCLUSION: These preliminary data suggest that a period of cognitive and physical rest may be a useful means of treating concussion-related symptoms, whether applied soon after a concussion or weeks to months later.