OBJECTIVE Copeptin, the C-terminal portion of provasopressin, has emerged as a novel prognostic marker in neurocritical care, such as in traumatic brain injury (TBI). The aim of this study was to quantitatively assess the prognostic significance of initial plasma copeptin levels in the neurological outcome and mortality after traumatic brain injury. METHODS Six relevant studies with data from 552 patients were included in this meta-analysis. RESULTS The plasma copeptin levels were found to be significantly higher in patients who died than in the survivors (standardized mean difference [SMD], 1.80). In the four studies reporting Glasgow outcome scale (GOS) data, patients with unfavorable outcomes had significantly higher copeptin levels than those with favorable outcomes (SMD, 1.62). The plasma copeptin level predicted mortality and unfavorable outcomes (AUC, 0.873; AUC, 0.876). CONCLUSIONS The present meta-analysis suggests that early measurement of plasma copeptin levels can provide better prognostic information about the functional outcome and mortality in patients with TBI.