BACKGROUND Spontaneous hemopneumothorax (SHP) is defined as the accumulation of >400 mL of blood in the pleural cavity in association with spontaneous pneumothorax. This rare clinical disorder may be life-threatening. METHODS A 71-year-old woman presented with a 1-month history of recurrent bloody stool, and electronic colonoscopy suggested a rectal mass. Laparoscopic radical resection of rectal cancer was performed. Two days later, she developed chest tightness, shortness of breath, and slight pain in the left chest. Emergency chest radiography revealed mild left pneumothorax and pleural effusion. SHP was suspected and a thoracic drain was inserted. However, the patient developed hemorrhagic shock 3 hours after drainage. She underwent emergency video-assisted thoracic surgery (VATS), which revealed left lung tip rupture with bleeding and adhesive band fracture at the top of the left thoracic cavity. The ruptured lung tissue was removed and electrocoagulation at the adhesion band was performed for hemostasis. The patient was discharged on postoperative day 11. At the time of this writing, she had developed no SHP recurrence or any other complications. CONCLUSIONS This case shows that conservative treatment may have serious consequences in patients with SHP. Thus, chest X-ray examination and VATS should be performed in patients with SHP.