Background: Traumatic pneumothoraces are a common consequence of major trauma. Despite this, there is a paucity of literature regarding their optimal management, including the role of conservative treatment. The aim of this study was to assess the treatment, complications, and outcomes of traumatic pneumothoraces in patients presenting to a major trauma center. Methods: The prospectively collected Trauma Audit and Research Network (TARN) database was used to identify all patients presenting with traumatic pneumothoraces to a UK major trauma center from April 2012 to December 2016. Demographics, mechanism of injury, injury severity score (ISS), management, and outcomes were analyzed. Results: Six hundred two patients were included during the study period. Mean age was 48 years (SD, 22 years), and 73% were men. Mean ISS was 26 and inpatient mortality was 9%. Of the 602 traumatic pneumothoraces, 277 of 602 (46%) were initially treated conservatively. Two hundred fifty-two of 277 patients in this cohort (90%) did not require subsequent chest tube insertion, including the majority of patients (56 of 62 [90%]) who were receiving positive pressure ventilation (PPV) on admission. The hazard ratio (HR) for failure of conservative management showed no difference between the ventilated and nonventilated patients (HR, 1.1; P =.84). Only the presence of a large hemothorax was associated with an increased likelihood of failure of conservative management. Conclusions: In the largest observational study of traumatic pneumothoraces published to date, > 90% of patients whose pneumothorax was managed conservatively never required subsequent tube drainage. Importantly, this also applies to patients requiring PPV, with no significant increased risk of failure of expectant management. These data support a role for conservative management in traumatic pneumothoraces.