Leech therapy, which can lead to complications such as anemia and bleeding, has been used to treat many diseases since ancient times. Furthermore, some substances in leech saliva are known to have anticoagulant effects. Acute mesenteric ischemia, which develops due to mesenteric vascular obstruction, can be treated medically or surgically. Non-occlusive mesenteric ischemia (NOMI) occurs as a result of decreased blood flow in mesenteric vessels due to hypovolemia, hypotension, etc. In this report, we mentioned a 57-year-old male patient who was admitted to the emergency department with syncope and weakness. In his medical history, the patient was stated to have used leech therapy to treat diabetic wounds on his feet, and prolonged and unstoppable bleeding was seen after leech bites. On his physical examination, there was tenderness in all quadrants of the abdomen. Abdominal computed tomography without contrast agent showed hepatic portal venous gas and pneumatosis cystoides intestinalis (PSI). The patient underwent laparotomy owing to the development of acute abdomen during the follow-up. Necrosis was seen in the terminal ileum and entire colon. Low flow in mesenteric vascular vessels of these necrotic segments was indicated with intraoperative Doppler ultrasonography. All necrotic segments were resected and open endileostomy was performed. The patient was discharged on the 17th day of follow-up. In conclusion, excessive bleeding caused by leech therapy can cause NOMI.