This study aims to determine if pairing the Glasgow Coma Scale (GCS) with serum biomarker levels may achieve higher outcome predictive values than using either the GCS or biomarker levels alone in childhood brain trauma. Twenty-eight critically ill children with isolated accidental brain trauma were studied in a prospective observational study. The GCS was recorded at various time points post injury. Enzyme-linked immunosorbent assay (ELISA) was used to quantify eight different serum biomarker levels (S100b, NSE, IL-6, IL-8, IL-10, L-selectin, SICAM, and endothelin) on day 1 post injury. The Glasgow Outcome Score (GOS) was used to assess global outcome at 6 months post injury. Outcome predictive values of the GCS, individual biomarker levels, and paired combinations of the GCS and biomarkers were compared using receiver operator characteristic (ROC) curve analysis and its multivariate extension, multivariate ROC curve (MultiROC). When using either the GCS or individual biomarker levels alone to predict unfavorable outcome, only the PICU discharge summated GCS achieved an area under the ROC curve (AUC) of more than 0.95. This high degree of outcome predictability was also achieved by pairing the GCS with a single biomarker level. The most pronounced improvement in outcome prediction was observed by pairing the post-resuscitation summated GCS with the day-1 serum IL-8 level, which increased the AUC from 0.78 to 0.98 and the sensitivity and specificity from 75% to 100% and 96% respectively. Paired combinations of the GCS and serum biomarker levels greatly enhanced the accuracy of post-traumatic unfavorable outcome prediction than may be achieved using either the GCS or individual biomarker levels alone.