Traumatic brain injury (TBI) is a craniocerebral trauma which causes long-term physical, cognitive and emotional impairment and adds substantially to the healthcare burden. The cost of TBIs is believed to be huge in Norway. Moderate and severe TBIs require rehabilitation, which helps reduce disability and improves the quality of life of patients. It is important to determine the efficacy of early rehabilitation as a form of treatment after severe TBI both in terms of its costs and effectiveness. A project entitled “Rehabilitation after severe traumatic brain injury” was introduced at Oslo University Hospital, Ulleval (OUH_U) in 2005, and the results showed that patients who received early rehabilitation had a better functional outcome than those who received later rehabilitation. However, as there are limited beds for early rehabilitation at the Intensive Care Unit (ICU), Oslo University Hospital, Ulleval, an assessment of the cost-effectiveness of early rehabilitation versus later rehabilitation is needed to ensure the best use of health care resources. The main purpose of this study is to find an optimal choice in terms of the cost-effectiveness of different treatments with or without early rehabilitation and to estimate the total hospitalization costs of moderate-to-severe TBI in the Eastern part of Norway.We developed a decision model to represent the two strategies after severe TBI and compared the incremental cost-effectiveness ratio (ICER) of early rehabilitation and later rehabilitation by measuring the costs and outcomes for both. The costs were estimated in diagnosis related group (DRG) prices, and the effect was estimated in the Glasgow Outcome Scale Extended (GOSE). The data source comes from the interviews, Patient Information System (Pasdoc) as well as NICEF.The analyses mainly show that the total five-year expected cost per TBI patient for early rehabilitation was NOK 1,236,542 and for later rehabilitation NOK 1,274,302. The GOSE gain from 3 months to 5 years was 22% higher with the continuous chain of treatment (1.43) when compared to that of the broken chain of treatment (1.17). The continuous chain of treatment was dominant in both effect and cost calculations. The ICE scatterplot demonstrated that the probability that early rehabilitation is the optimal alternative was 61.6% in the model.The findings indicate that early rehabilitation after TBI represents a dominant strategy in that it reduces costs and improves outcomes under reasonable assumptions.