Background: Heterotopic pregnancy is the coexistence of intrauterine and extrauterine (ectopic) pregnancies. This is a relatively rare phenomenon with an incidence of 1 in 30,000 in spontaneously conceived pregnancies and 1 in 100 pregnancies achieved through assisted reproduction. Due to its relative rarity, diagnosis can be challenging. The presence of adnexal cystic masses complicating pregnancies can obscure the examination of the pelvis to rule in/out heterotopic pregnancy further adding to the complexity of the diagnosis. Case Presentation: In this study, we present a 26-year-old primigravid, ethnic Tigrayan lady from the Tigray region of Ethiopia. She presented to our hospital with the complaint of progressively worsening abdominal pain of three days duration. She also had a subjective period of amenorrhea of 2 months duration. Pregnancy test was positive a few days prior to her current presentation. She reported that she had a history of treatment for pelvic inflammatory disease three months prior to her current conception. At presentation to our hospital, she was acutely ill-looking in pain, tachycardic, and hypotensive. Pelvic ultrasound showed an adnexal mass, hemoperitoneum, and an intrauterine pregnancy at 7 weeks + 5 days gestation. With the impression of ruptured ovarian cyst to rule out heterotopic pregnancy emergency, an explorative laparotomy was done which was pertinent for significant hemoperitoneum, ruptured left tubal ectopic pregnancy, and intact left ovarian cyst. Conclusion: Physicians should consider a broad range of differential diagnosis in pregnant mothers who present with acute abdominal pain. Moreover, in the presence of an adnexal mass and hemoperitoneum, there is a need to maintain a low threshold for rare but life-threatening complications such as heterotopic pregnancy. The presence of an intrauterine gestation does not rule out extrauterine gestation. Thus, the presence of a viable intrauterine gestation should not stop physicians from carefully examining patients for the coexistence of an ectopic pregnancy.