Objective:To explore the correlation of serum albumin level at admission with clinical prognoses in patients with acute traumatic brain injury (TBI).Methods:One hundred and fifty-four patients with acute moderate-extreme severe TBI (Glasgow Coma Scale [GCS] scores of 3-12 at admission) in Department of Neurosurgery, General Hospital of Western Theater Command from January 1, 2019 to December 31, 2020 were chosen. The comprehensive clinical data of these patients were collected, including age, gender, GCS scores, serum albumin level (hypoalbuminemia defined as<35 g/L), hemoglobin level, comorbidities, treatment measures, and prognoses 6 months after discharge (poor prognosis defined as Glasgow outcome Scale [GOS] scores of 1-2, and good prognosis defined as GOS scores of 3-5). Univariate and multivariate Logistic regressions were used to identify the independent factors for clinical prognoses of these patients, and differences in poor prognosis rate, length of ICU stay, and total hospital cost were compared between different groups.Results:Among the 154 patients, 43 had poor prognosis and 111 had good prognosis. Serum albumin level at admission ( OR=0.916, 95% CI: 0.843-0.996, P=0.001) and GCS scores at admission ( OR=0.701, 95% CI: 0.594-0.828, P<0.001) were independent factors for prognosis. Patients with hypoalbuminemia ( n=70) displayed significantly higher poor prognosis rate, longer ICU stays, and increased total hospitalization cost compared with those without hypoalbuminemia ( n=84, P<0.05); specifically, in patients with GCS scores of 9-12 at admission ( n=58), those with hypoalbuminemia ( n=27) exhibited significantly higher poor prognosis rate, longer ICU stays, and higher total hospitalization cost than their non-hypoalbuminemia counterparts ( n=31, P<0.05); similarly, in patients with GCS scores of 3-8 at admission ( n=96), those with hypoalbuminemia ( n=74) had significantly higher poor prognosis rate than their non-hypoalbuminemia counterparts ( n=22, P<0.05). In patients with good prognosis, those with hypoalbuminemia ( n=56) showed significantly longer total hospital stays, prolonged ICU stays, and increased total hospitalization cost compared with those without hypoalbuminemia ( n=55, P<0.05). Conclusion:Low serum albumin level at admission is likely to lead to poor prognosis, prolonged ICU stays and increased total hospitalization cost in patients with acute TBI.