The incidence of heterotopic/ectopic pregnancy has risen in recent years, largely due to more frequent use of ovulatory medicine and increased incidence of pelvic inflammatory disease. In a natural cycle, it is a very rare event. Most heterotopic/ectopic pregnancies are localized in the uterine tube and, usually, it is diagnosed when symptoms develop. We report the case of a 37 year-old, gravida 2, para 0, abortion 1 woman with no known risk factors for heterotopic pregnancy. The patient attended the emergency department because of acute abdominal pain. She was evaluated in our department and a heterotopic twin pregnancy in the tube was diagnosed by transvaginal sonography. Intrauterine pregnancy with positive fetal cardiac activity at 9 weeks of gestation according to crown-rump length measurement was detected. Laparotomy was carried out because of acute abdominal syndrome. Right ruptured tubal ectopic/heterotopic pregnancy and hemoperitoneum were diagnosed. Right salpingectomy was carried out. Pathology revealed monochorionic twin tubal pregnancy. In a review of the literature, this is first case of twin tubal pregnancy in one uterine tube. In conclusion, heterotopic pregnancy in twin form in the uterine tube is possible in natural cycles. Intrauterine pregnancy does not exclude extrauterine pregnancy in natural cycles.