The incidence of minor and mild to moderate traumatic brain injuries (TBI) have increased in the recent years, mainly at the expense of grave and moderate to severe injuries. The protein S100 β is a sensitive biomarker to head injury. The aim of this study is to investigate importance of S100 β protein as a new biomarker yielding a more informative diagnostic and prognostic technique to be added to the working protocols of dealing with TBIs. Fifty one patients with mild or moderate head injury were included in this study. Sociodemographic data, clinical data and computerized tomography (CT) findings were recorded in addition to measuring serum S100 β levels within 6 hours after trauma. There was a significant increase of S100 β levels in non survivors compared with survivors (P <0.001). There was a significant negative correlation between the levels of S100 β and survival period in cases that died (r = -0.887, P <0.001). The protein S100 β had a good predictive power for mortality (AUC = 0.803, cut off value > 1.205 ug/L, sensitivity = 100%, specificity = 54.55%). Adding S100 β levels to Glasgow coma score and CT scan findings increased the accuracy of prediction of outcome from 64.7% to 82.4%. However, there were no significant differences in S100 β levels as regards categories of severity or types of CT findings. It could be concluded that S100 β serum level is a good predictor of outcome in cases of mild and moderate head injuries and its use is recommended both in clinical guidelines and in forensic practice.