Background <p>Guidelines recommend prophylactic chest tube placement in patients with traumatic pneumothorax who require positive pressure ventilation to prevent tension pneumothorax. However, chest tube insertion is not without complications, and avoiding it when safely possible is desirable.</p> Case presentation <p>A man in his 50 s with a left clavicle fracture and mild left-sided occult pneumothorax on computed tomography was scheduled for surgery under general anesthesia. Conservative management was chosen given the absence of respiratory symptoms and stable imaging. To minimize the risk of pneumothorax progression during positive pressure ventilation, one-lung ventilation was employed to avoid ventilating the affected lung. Surgery proceeded uneventfully, with transient hypoxemia that was managed by increasing FiO₂ to 100%. Postoperative imaging confirmed re-expansion of the left lung and no pneumothorax progression. The patient was discharged in good condition.</p> Conclusions <p>General anesthesia was safely managed without prophylactic chest tube placement by employing one-lung ventilation in a patient with occult traumatic pneumothorax.</p>