Background: Traumatic brain injury (TBI) is a one of the commonest injuries treated at the Neurosurgery Department. The incidence rate is approximately 3% in the general population and the mortality rate is about 30% of all injury deaths. Hyponatremia leads to high morbidity and/or mortality in TBI patients. Our study discusses the epidemiology of TBI associated with hyponatremia. Methods: Retrospective analysis of 80 patients with TBI between February 2017 and November 2018 was performed. The relationship between the incidence of hyponatremia in TBI patients and age, sex, GCS, type, severity of injury and whether the patient was submitted to surgery or not. Results: Out of 80 TBI patients recruited for the study, 25 of them suffered from hyponatremia. Hyponatremia following TBI wasn't related to age, sex but it was related to the type of injury, the Glasgow Coma Scale (GCS) score ≤ 8, surgical history. TBI with hyponatremia usually had longer stay in the hospital and bad outcome. Conclusions: Sever TBI patients (GCS score ≤ 8), intracranial hemorrhage and/or skull base fracture are susceptible to developing hyponatremia and require additional treatment aiming to normalization of serum sodium levels to prevent deterioration of their condition. Abbreviations: ANP, Atrial natriuretic peptide; CSWS, Cerebral salt wasting syndrome; SIADH, Syndrome of inappropriate secretion of antidiuretic hormone; TBI, Traumatic brain injury