We here report the first case of discordant Pena–Shokeir phenotype observed in monoamniotic twins. A 34-year-old woman, pregnant with twins, was referred at 10 weeks' gestation because one of the twins had increased nuchal translucency. Serial ultrasonographic examinations suggested that twin A may have had several other abnormalities, including pleural effusion at 21 weeks' gestation, decreased movement and contracted limbs at 24 weeks, and fetal growth restriction at 26 weeks. No abnormalities were observed in twin B. At 34 weeks of gestation, the twins were delivered by cesarean section. There were cord entanglements, and although the resuscitation of twin A was attempted, it proved difficult due to lockjaw. Twin A died during the second hour of life, and autopsy findings were consistent with the diagnosis of Pena–Shokeir phenotype. We suggest that cord entanglement during early gestation is a possible cause for the occurrence of Pena–Shokeir phenotype through an anoxic-ischemic mechanism.