Severely injured trauma patients are often coagulopathic and early hemostatic resuscitation is essential. Previous studies have revealed linear relationships between thrombelastography (TEG^®) five- and ten-min amplitudes (A5 and A10), and maximum amplitude (MA), using TEG^® 5000 technology. We aimed to investigate the performance of A5 and A10 in predicting low MA in severely injured trauma patients and identify optimal cut-off values for hemostatic intervention based on early amplitudes, using the cartridge-based TEG^® 6s technology. Adult trauma patients with hemorrhagic shock were included in the iTACTIC randomized controlled trial at six European Level I trauma centers between 2016 and 2018. After admission, patients were randomized to hemostatic therapy guided by conventional coagulation tests (CCT) or viscoelastic hemostatic assays (VHA). Patients with available admission-TEG^® 6s data were included in the analysis, regardless of treatment allocation. Low MA was defined as <55 mm for Kaolin TEG^® and RapidTEG^®, and <17 mm for TEG^® functional fibrinogen (FF). One hundred eighty-seven patients were included. Median time to MA was 20 (Kaolin TEG^®), 21 (RapidTEG^®) and 12 (TEG^® FF) min. For Kaolin TEG^®, the optimal Youden index (YI) was at A5 < 36 mm (100/93% sensitivity/specificity) and A10 < 47 mm (100/96% sensitivity/specificity). RapidTEG^® optimal YI was at A5 < 34 mm (98/92% sensitivity/specificity) and A10 < 45 mm (96/95% sensitivity/specificity). TEG^® FF optimal YI was at A5 < 12 mm (97/93% sensitivity/specificity) and A10 < 15 mm (97/99% sensitivity/specificity). In summary, we found that TEG^® 6s early amplitudes were sensitive and specific predictors of MA in severely injured trauma patients. Intervening on early amplitudes can save valuable time in hemostatic resuscitation.