OBJECTIVE Treadmill test protocols for concussion assessment have been validated for patients aged 13 years and older; however, no evidence-based guidelines exist for younger children. We designed and assessed the safety and utility of the Morahan Pediatric Concussion Exercise Tolerance Test (MPCETT) for assessing exercise tolerance in symptomatic children (SC) and recovered, asymptomatic children (AC) from 6 to 12 years of age. METHODS Retrospective case series. METHODS Secondary care center. METHODS Children were diagnosed with concussion using consensus guidelines. At assessment, SC [n = 17; median (range) 10 (6-12) years; 18% female; 28 (13-50) days since injury] had persistent concussive symptoms, while AC [n = 24; 9 (7-12) years; 21% female; 21 (8-37) days since injury] required assessment for return to activity. METHODS The MPCETT is a modified Buffalo Concussion Treadmill Test for pediatric populations. The test was administered to establish exercise tolerance and was terminated for increased symptoms or self-reported exhaustion. METHODS Presence of adverse events and exercise intolerance. RESULTS The number of adverse events was 0 in both groups. Exercise intolerance occurred in 64.7% (95% CI, 38.3%-85.8%) of children within the SC group versus 12.5% (95% CI, 2.7%-32.4%) within the AC group ( P < 0.001). CONCLUSIONS Pediatric exercise tolerance testing is safe and effective for assessing exercise intolerance in concussed children.