Uterus didelphys is an uncommon Müllerian duct anomaly that may be overlooked when one hemiuterus is gravid and the contralateral hemiuterus is mistaken for a leiomyoma. We report a 25-year-old G5P2A2 woman who presented with one week of vaginal bleeding, reduced fetal movement, lower abdominal pain, and absent fetal heart activity. A prior two-dimensional ultrasound had described a uterine myoma, and no three-dimensional ultrasound or magnetic resonance imaging had been performed. At emergency cesarean delivery, two distinct uterine bodies were identified, confirming uterus didelphys; the clinical record also documented cervical duplication. A 1300-g female fetus was delivered without signs of life, and no corrective metroplasty was performed. This case emphasizes that two-dimensional ultrasonography may be insufficient when uterine contour is atypical and that definitive characterization requires assessment of both the internal cavity and external fundal contour, preferably with three-dimensional transvaginal ultrasound or magnetic resonance imaging. Although uterus didelphys does not necessarily reduce fertility, it is associated with higher risks of preterm birth, malpresentation, cesarean delivery, and other adverse perinatal outcomes. Preconception anatomical confirmation, early pregnancy surveillance, and individualized counseling are therefore essential in subsequent pregnancies.