The aim of the study was to determine whether serum levels of hyperphosphorylated neurofilament NF-H correlate with severity of brain injury in children. Methods: Forty-nine patients with traumatic brain injury (TBI) were enrolled into the prospective study. Venous blood samples were taken after admission and every 24 h for a maximum of 6 consecutive days. Serum NF-H concentrations were quantified by enzyme-linked immunosorbent assay. The outcome was evaluated 6 months after TBI using Glasgow Outcome Scale (GOS) in all patients. Results: The quantitative level of pNF-H remained significantly higher in patients with poor outcome (GOS = 1) in comparison with the other patients for the 2nd-4th day (p = 0.027; p = 0.019; p = 0.01). Levels of pNF-H were significantly higher in patients with diffuse axonal injury on initial CT scan (p = 0.004). Normal levels pNF-H in the paediatric population are unknown. Objective ROC analysis was identification of optimal cut-offs of proteins for prediction of GOS = 1. Conclusions: Although further, prospective study is warranted, these findings suggest that levels of hyperphosphorylated neurofilament NF-H correlate with mortality and may be useful as predictors of outcome in children with TBI.