Blunt abdominal trauma is not uncommon, but traumatic small intestine perforation in the incisional hernia is very rare. Diagnosis is sometimes difficult. We present a patient who had undergone surgical resection of gastrointestinal stromal tumor (GIST) and sustained an incisional hernia with a segment of intestine falling into the right lower quadrant of the abdomen. He was kicked over the hernia and then sustained progressive severe pain. At the emergency department, an impression of peritonitis was made, and bladder rupture was highly suspected after obtaining an abdominal CT scan. Small intestine perforation was confirmed during emergency laparotomy. Due to lack of protection by the intact belly, the small intestine in the hernia sac is vulnerable to injury under direct contusion. Besides, accumulation of the intestinal content around the lower abdominal cavity may mask the manifestations of perforation and lead to the misdiagnosis of urinary bladder rupture. Therefore, one should be aware that hernia is a risk factor of small intestine perforation. Physicians should not forget the possibility of the risk of small intestine perforation in patients with hernia who sustain blunt abdominal contusion.