Aim:Oxidative stress(OS) and lipid peroxidation(LP) occur in a cell due to irreversible damage resulting from incidents such as traumatic brain injury(TBI). The aim of our study was to investigate the possible neuroprotective effect of boric acid (BA) by examining the changes in catalase (CAT) activity and levels of CAT and malondialdehyde (MDA) in brain tissues from rats with closed head trauma.Material and Methods:The study consisted of three groups: control ,TBI and TBI + BA. Animals in the control and TBI groups received saline ,while animals in the TBI + BA group received BA through daily oral gavage, for 14 days prior to TBI was performed using the modified Marmarou impact acceleration model . After 24 hours,animals were euthanized and brain tissue obtained to measure the levels of MDA and to assess the activity of CAT. Results:MDA levels and CAT activity were significantly higher in the TBI group versus the control group. However, they were significantly lower in the TBI + BA group compared to TBI alone. Similarly, edema and necrotic neurons were observed in the TBI group, but not in the control or TBI + BA groups.Conclusion:Based on biochemical and histopathological evidence, we determined that TBI induced LP and OS were inhibited by pre-treatment with BA.