Background: Acute Traumatic Coagulopathy (ATC) is a complex pathological process that is associated with patient mortality and increased blood transfusion requirements. It is evident on hospital arrival, but there is a paucity of information about the nature of ATC and the characteristics of patients that develop ATC in the pre-hospital setting. The objective of this study was to describe the nature and timing of coagulation dysfunction in a cohort of injured patients and to report on patient and pre-hospital factors associated with the development of ATC in the field. Methods: This was a prospective observational study of a convenience sample of trauma patients. Patients had blood taken during the pre-hospital phase of care and evaluated for derangements in Conventional Coagulation Assays (CCA) and Rotational Thromboelastometry (ROTEM). Associations between coagulation derangement and pre-hospital factors and patient outcomes were evaluated. Results: A total of 216 patients who had either a complete CCA or ROTEM were included in the analysis. One hundred and eighty (83 %) of patients were male, with a median injury severity score of 17 [interquartile range (IQR) 10–27] and median age of 34 years [IQR = 25.0–52.0]. Hypofibrinogenemia was the predominant abnormality seen, (CCA Hypofibrinogenemia: 51/193, 26 %; ROTEM hypofibrinogenemia: 65/204, 32 %). Increased CCA derangement, the presence of ROTEM coagulopathy, worsening INR, worsening FibTEM and decreasing fibrinogen concentration, were all associated with both mortality and early massive transfusion. Conclusion: Clinically significant, multifaceted coagulopathy develops early in the clinical course, with hypofibrinogenemia being the predominant coagulopathy. In keeping with the ED literature, pre-hospital coagulation dysfunction was associated with mortality and early massive transfusion. Further work is required to identify strategies to identify and guide the pre-hospital management of the coagulation dysfunction seen in trauma.