Pneumothorax as a complication of pleural catheter insertion could be very dangerous in patients under mechanical ventilation. In ICU patients, physical examination and supine chest x-ray (CXR) are poorly sensitive in diagnosis of pneumothorax. Moreover, CT scan has also disadvantages, such as radiation, high cost, time consuming and need for patient transfer to radiology suit. In comparison to CXR and CT scan, ultrasonography is an available tool for early and rapid detection of this complication. In this study, we reported a 21-year-old woman, a victim of trauma, undergone pleural catheter insertion for drainage of hemothorax. She developed pneumothorax after the procedure. We discuss the usefulness of ultrasonography after pleural catheter insertion and concluded its adequacy and effectiveness in early diagnosis and also follow-up of pneumothorax.