The effect of mild hypothermia therapy (34°-36°C) and alterations of matrix metalloproteinase-9 (MMP-9) were examined in 20 patients with high risk traumatic brain injury (TBI). The neurologic status was assessed using the Full Outline of UnResponsiveness (FOUR) score and the outcome using the Marshall CT score. The objective of this study was to determine serum MMP-9 level and the Marshall CT score. This research used a prospective randomized controlled study and was conducted in RD Kandou Hospital Manado. Patients with high risk TBI (the FOUR score ≤7) were randomized into two groups, with and without mild hypothermia therapy, and were investigated within 24 and 72 hours. The MMP-9 protein levels were estimated using enzyme-linked immunosorbent assay (ELISA). Different levels of these variables were compared in the two groups. The results showed that the level of MMP-9 protein significantly decreased (p<0.05) in the hypothermia group; however, there was no significant improvement of the Marshall CT score (p>0.05) within 24-72 hours. The study concluded that mild hypothermia therapy had a significant influence on the alteration of biomarkers rather than the alteration of anatomical imaging in high risk TBI patients.