We describe the incidence and etiology of fever and the relationship between fever characteristics and outcome in children with severe traumatic brain injury (TBI). We conducted a retrospective study of children <14 years and with Glasgow Coma Scale (GCS) score of <9 admitted to a level I pediatric trauma center intensive care unit (PICU) between 1998 and 2003. We examined whether fever characteristics were associated with poor outcome (hospital discharge GCS score <13 and discharge disposition of either death or discharge to a skilled nursing facility). PICU length of stay (LOS) and hospital LOS were also examined. Data are presented as means and medians (SD), and P < 0.05 reflects significance. Ninety-three records were reviewed. Patients were 5.7 (SD 4.1) years old, 70% were male, and the average admission GCS score was 5. Mortality rate was 14%. Forty-eight (52%) patients had fever, and 23 (48%) of those patients had infectious fever. Each additional febrile episode was associated with a twofold higher risk of patients having a hospital discharge GCS score of <13 (odds ratio 2.4, 95% confidence interval 1.2-5.0) and having a 0.4-day longer PICU LOS (P < 0.001). Patients with infectious fever had a 0.9-day longer PICU LOS (P < 0.001). Patients with any fever in the PICU had an increased HLOS (0.9 days; P < 0.001). Our data suggest that in severe pediatric TBI, both fever and infection were common, and both were associated with longer LOS. Patients with higher fever burden had poor hospital discharge GCS score.