The occurrence of a pneumothorax using supraglottic device is a rare complication during general anesthesia. Moreover, less than 2% of pneumothoraxes can be related to lung metastases, most due to soft tissue sarcoma. We present the case of a 45-year-old female diagnosed with metastatic sarcoma who developed a bilateral pneumothorax after general anesthesia with supraglottic device. Different causes of pneumothorax were discussed.