Coagulation assessment in traumatic brain injury (TBI) typically relies upon laboratory-based standard coagulation tests (SCTs), including the activated partial thromboplastin time (aPTT), INR and platelet count. Rotational thromboelastometry (ROTEM) sigma is an alternative point-of-care assay; however, its role in isolated TBI is under-evaluated. The present study aims to assess the prognostic utility of ROTEM sigma in isolated TBI. ROTEM sigma analysis was performed during the initial evaluation of patients presenting to the Royal Adelaide Hospital between February 2022 and 2023 with radiographically demonstrated traumatic intracranial haemorrhage and GCS ≤14. Patients with concomitant severe extracranial injury, or who received blood products or antifibrinolytic therapy prior to sample collection were excluded. Thirty-six patients had blood samples analysed with ROTEM, 25 of these patients were also evaluated with paired SCTs. Twenty-two per cent (8/36) of patients with isolated TBI had a hypocoaguable ROTEM profile, and this was associated with an increased incidence of head injury-related death (50% [4/8] vs 11% [3/28], P = 0.03). Median diagnostic turn-around-times were shorter for ROTEM parameters compared to SCT counterparts: EXTEM clotting time (CT) versus INR (20 vs 63 min, P < 0.01), and INTEM CT versus aPTT (21 vs 63 min, P < 0.01). EXTEM CT, FIBTEM CT and INR values had similar performance in predicting head injury-related death, area under the receiver operator curves were 0.8, 0.8 and 0.7, respectively. ROTEM sigma expedites the detection of clinically significant coagulopathy in isolated TBI. EXTEM and FIBTEM CT values are more rapidly attainable than INR and comparable in predicting head injury-related death.