Introduction: Rudimentary horn pregnancy (RHP), an entity with a diagnostic dilemma is known to rupture most commonly in second trimester, sometimes in early third trimester. This case of ectopic rudimentary horn (RH) presented acutely in the first trimester. Case Presentation: A 30 years old G 3 P 2 L 2 with previous two vaginal deliveries presented with acute abdominal pain and features of hemorrhagic shock at 8 weeks 5 days gestational age. With clinical diagnosis of ruptured ectopic pregnancy, the patient immediately underwent laparotomy, which revealed hemoperitoneum with a unicornuate uterus along with ruptured RHP. RH excision with ipsilateral salpingectomy and right tubal ligation was done and the maternal life salvaged. Conclusion: High index of suspicion based on clinical history and examination complemented with diagnostic radiological modalities can help in prenatal and pre-rupture diagnosis of RHP, hence its prompt treatment to alleviate scope of any emergency situation and the disastrous consequences leading to maternal morbidity and mortality.