Purpose: To report a case of ruptured uterus in the first trimester with the use of misoprostol for early pregnancy failure in a woman with unrecognized cesarean section scar pregnancy. Case: A 27-year-old woman, gravida 5 para 3+1, presented with abdominal pain and vaginal bleeding. Transvaginal ultrasonography revealed a fetus without fetal heart activity at nine weeks gestation, making the diagnosis of early pregnancy failure. Her previous deliveries were by cesarean section. She was managed medically with misoprostol. Seven hours after misoprostol administration, she developed sudden onset of severe abdominal pain. Repeat transvaginal ultrasonography diagnosed cesarean section scar pregnancy. Laparotomy revealed hemoperitoneum with rupture of cesarean section scar pregnancy. Subtotal hysterectomy was performed. Conclusions: Failure to recognize cesarean section scar pregnancy can result in a ruptured uterus in the first trimester with the use of misoprostol for early pregnancy failure. Increased awareness of the unexpected consequences of cesarean section is of paramount importance.