Pneumothorax in critically ill patients remains a common problem in the ICU, occurring in 4% to 15% of patients. Pneumothorax should be considered a medical emergency and requires a high index of suspicion, prompt recognition, and intervention. The diagnosis of pneumothorax in the critically ill patient can be made by physical examination findings or radiographic studies including chest radiographs, ultrasonography, or CT scanning. Ultrasonography is emerging as the diagnostic procedure of choice for the diagnosis and management guidance and management of pneumothoraces, if expertise is available. Pneumothoraces in unstable, critically ill patients or in those on mechanical ventilation should be managed with tube thoracostomy. If there is suspicion for tension pneumothorax, immediate decompression and drainage should be performed. With widespread use of CT scanning, there have been more occult pneumothoraces diagnosed, and the most recent literature suggests that drainage is preferred. In patients with a persistent air leak or failure of the lung to expand, current guidelines suggest that an early thoracic surgical consultation be requested within 3 to 5 days.