Background: Chest trauma was the third most common cause of death in polytrauma patients, accounting for 25% of all deaths from traumatic injury. Chest trauma involves in injury to the bony thorax, intrathoracic organs and thoracic medulla. This study aimed to investigate the incidence, clinical characteristics, and outcome of polytrauma patients with pulmonary contusion, flail chest and upper thoracic spinal injury. Methods: Patients who met inclusion criteria were divided into groups: Pulmonary contusion group (PC); Pulmonary contusion and flail chest group (PC + FC); Pulmonary contusion and upper thoracic spinal cord injury group (PC + UTSCI); Thoracic trauma triad group (TTT): included patients with flail chest, pulmonary contusion and the upper thoracic spinal cord injury coexisted. Outcomes were determined, including 30-day mortality and 6-month mortality. Results: A total 84 patients (2.0%) with TTT out of 4176 polytrauma patients presented to Tongji trauma center. There was no difference in mean ISS among PC + FC group, PC + UTSCI group and TTT group. Patients with TTT had a longer ICU stay (21.4 days vs. 7.5 and 6.2; p<0.01), relatively higher 30-day mortality (40.5% vs. 6.0% and 4.3%; p<0.01), and especially higher 6-month mortality (71.4% vs. 6.5%, 13.0%; p<0.01), compared to patients with PC + FC or with PC + UTSCI. The leading causes of death for patients with TTT were ARDS (44.1%) and pulmonary infection (26.5%) during first 30 days after admission. For those patients who died later than 30 days during the 6 months, the predominant underlying cause of death was MOF (53.8%). Conclusions: Lethal triad of thoracic trauma (LTTT) were described in this study, which consisting of pulmonary contusion,flail chest and the upper thoracic spine cord injury. Like the classic "lethal triad", there was a synergy between the factors when they coexist, resulting in especially high mortality rates. Polytrauma patients with LTTT were presented relatively high 30-day mortality and 6 months mortality. We should pay much more attention to the patients with LTTT for further minimizing complications and mortality. (C) 2021 Elsevier Ltd. All rights reserved.