Objectives: To determine (1) the presence of fatigue symptoms and predictors of fatigue after childhood brain injury and examine (2) the feasibility, reliability, and validity of a multidimensional fatigue measure (PedsQL Multidimensional Fatigue Scale [MFS]) obtained from parent and child perspectives. Setting: Emergency and intensive care units of a hospital in Melbourne, Australia. Participants: Thirty-five families (34 parent-proxies and 32 children) aged 8 to 18 years (mean child age = 13.29 years) with traumatic brain injury (TBI) of all severities (27 mild, 5 moderate, and 3 severe) admitted to the Royal Children’s Hospital. Design: Longitudinal prospective study. Fatigue data collected at 6-week follow-up (mean = 6.9 weeks). Main Outcome Measures: Postinjury childand parent-rated fatigue (PedsQL MFS), mood, sleep, and pain based on questionnaire report: TBI severity (mild vs moderate/severe TBI). Results: A score greater than 2 standard deviations below healthy control data indicated the presence of abnormal fatigue, rates of which were higher compared with normative data for both parent and child reports (47% and 29%). Fatigue was predicted by postinjury depression and sleep disturbance for parent, but not child ratings. Fatigue, as rated by children, was not significantly predicted by TBI severity or other symptoms. The PedsQL MFS demonstrated acceptable measurement properties in child TBI participants, evidenced by good feasibility and reliability (Cronbach alpha values >0.90). Interrater reliability between parent and child reports was poor to moderate. Conclusions: Results underscore the need to assess fatigue and associated sleep-wake disturbance and depression after child TBI from both parent and child perspectives.