Background: The most common cause of death in cases of pelvic trauma is exsanguination caused by associated injuries but not the pelvic injury per se. For patients with relatively isolated pelvic trauma, the impact of the vascular injury severity on the outcome remains unclear. We hypothesized that, in addition to the fracture pattern complexity, the severity of the pelvic vascular injury plays a more decisive role in the outcome. Methods: The medical records of patients with pelvic fracture at a single center between Jan 2016 and Dec 2017 were retrospectively reviewed. Those with an abbreviated injury scale (AIS) score ≥3 in areas other than the pelvis were excluded. Lateral compression (LC) type 1 fractures and anteroposterior compression (APC) type 1 fractures according to the Young-Burgess classification and ischial fractures were defined as simple pelvic fractures, while other fracture types were considered complicated pelvic fractures. Based on CT, the vascular injury severity was defined as minor (fracture with or without hematoma) or severe (hematoma with contrast pooling/extravasation). The patient demographics, clinical parameters, and outcome measures were compared between the groups. Results: Twenty-six of the 155 patients had a severe vascular injury. Those with severe vascular injuries had poorer hemodynamics, a higher injury severity score (ISS), required more blood transfusions, and had a longer ICU stay (3.81 vs. 0.86 days, p=0.000) and total hospital stay (20.7 vs. 10.1 days, p=0.002) than those with minor vascular injuries. In contrast, those with complicated pelvic fractures (LC II/III, APC II/III, vertical shear and combined type fracture) required a similar number of transfusions and had a similar length of ICU stay compared to those with simple pelvic fractures (LC I, APC I and ischium fracture), but they had a longer total hospital stay (13.6 vs. 10.3 days, p=0.034). These findings were similar even if only patients with an ISS >=16 were considered. Conclusions: Our results indicate that even in patients with relatively isolated pelvic injuries, the vascular injury severity is more closely correlated to the outcome than the type of anatomical fracture. Therefore, a more balanced classification of pelvic injury that takes both the fracture pattern and hemodynamic status into consideration, such as the WSES classification, seems to have better utility for clinical practice.