Purpose: Previously, higher circulating levels of matrix metalloproteinase (MMP)-9 and tissue inhibitor matrix metalloproteinases (TIMP)-1 were reported in the first hours after TBI in blood samples from patients with poor prognosis. Thus, the objectives of this study were to determine whether MMP-9 and TIMP-1 levels during the first week of a severe TBI could be used as biomarker predictive of mortality. Methods: We included patients with severe TBI (defined as Glasgow Coma Scale lower than 9), and with Injury Severity Score in non-cranial aspects lower than 9. We determined serum concentrations of MMP-9 and TIMP-1 at days 1, 4 and 8 of TBI. Results: TIMP-1 concentrations at days 1 (p < .001), 4 (p = .001), and 8 (p = .01) of TBI were higher in nonsurviving (n = 34) than in surviving (n = 90) patients. ROC curve analyses showed an area under curve of TIMP-1 concentrations at days 1, 4, and 8 of TBI to predict 30-day mortality of 78% (p < .001), 76% (p <.001) and 71% (p= .02) respectively. Conclusions: The most relevant new findings of our study were that TIMP-1 levels during the first week of a severe TBI were higher in non-surviving than in surviving patients and that could be used as biomarker predictive of mortality. (C) 2019 Elsevier Inc. All rights reserved.