Background: Laboratory-based evidence of coagulopathy (LC) is observed in 25-35% of trauma patients, but clinically-evident coagulopathy (CC) is not well described. Methods: Prospective observational study of adult trauma patients transported by helicopter from the scene to nine Level 1 trauma centers in 2015. Patients meeting predefined highest-risk criteria were divided into CC+ (predefined as surgeon-confirmed bleeding from uninjured sites or injured sites not controllable by sutures) or CC-. We used a mixed-effects, Poisson regression with robust error variance to test the hypothesis that abnormalities on rapid thrombelastography (r-TEG) and international normalized ratio (INR) were independently associated with CC+. Results: Of 1,019 highest-risk patients, CC+ (n=41, 4%) were more severely injured (median ISS 32 vs 17), had evidence of LC on r-TEG and INR, received more transfused blood products at 4 hours (37 vs 0 units), and had greater 30-day mortality (59% vs 12%) than CC- (n=978, 96%). The overall incidence of LC was 39%. 30-day mortality was 22% vs 9% in those with and without LC. In two separate models, r-TEG K-time >2.5 min (RR 1.3, 95% CI 1.1-1.7), r-TEG mA <55 mm (RR 2.5, 95% CI 2.0-3.2), platelet count <150 x 109/L (RR 1.2, 95% CI 1.1-1.3), and INR >1.5 (RR 5.4, 95% CI 1.8-16.3) were independently associated with CC+. A combined regression model was not generated because too few patients underwent both r-TEG and INR. Conclusion: CC was rare compared to LC. CC was associated with poor outcomes and impairment of both clotting factor and platelet-mediated coagulation components.