Bevacizumab added to 5-fluorouracil-based chemotherapy can improve outcomes in patients with metastatic colorectal cancer. Bevacizumab had several notable adverse effects including bowel perforation but pneumothorax had never been reported in the available English literature. We reported a 45-year-old male with lung metastases from colorectal cancer who had spontaneous pneumothorax after the second cycle of bevacizumab-containing chemotherapy. His pneumothorax resolved after tube thoracostomy with a small caliber catheter. The mechanism of pneumothorax developed after bevacizumab therapy was not clear as bowel perforation but tumor necrosis with ruptured parietal pleura might be the cause. In patients who had chest discomfort after bevacizumab-containing therapy, pneumothorax should never be overlooked as one of the differential diagnoses.