BACKGROUND: Severe head injury is a major public health threat that is the main cause of morbidity and mortality in all age groups of the world’s populations including Ethiopia. In view of this, this study was assessed the severity of head injury and its contributing factors. METHODS: A Two-year retrospective study was conducted at Dilla University Referral Hospital, from December 2014 to November 2016. All head injury patients admitted to the surgical ward were included. Bivariate and multivariate regression analyses were used to identify factors associated with severity of head injury. RESULTS: A total of 106 eligible head injury patient charts were reviewed. The magnitude of severe head injury was 32.1%. Young populations, mainly males, were the highest risk groups, and road traffic accident was the main cause of severe head injury. In adjusted analysis, age interval greater than 45 years (aOR, 5.41; 95% CI:1.05-29.09), alcohol consumption before the trauma (aOR, 4.16, 95%CI: 1.18, 14.61), delayed presentation (beyond 24 hours) after injury (aOR, 4.717; 95% CI: 1.02-21.81), and respiratory rate greater than 30 breaths per minute (aOR, 7.34; 95% CI: 1.88-28.73) were significantly associated with severe head injury. CONCLUSIONS: Severe head injury remains an important public health problem. Young adults were the highest risk groups of populations. Prevention of road traffic accidents, continuous awareness creation about the consequences of road traffic accident and close neurological monitoring offered by neuro-intensive care unit are recommended.KEYWORDS: Head Injury, Glasgow Coma Scale, Severe Head Injury