We present a case of monochorionic-diamniotic (MD) twin pregnancy with polyhydramnios-polyhydramnios sequence. A 20-year-old woman, gravida 1, para 0, was referred to our hospital at 31 weeks and 6 days' gestation for consultation about a high-risk pregnancy due to the presence of discordant fetal growth pattern (26% of fetal growth discordance) with polyhydramnios in MD twin pregnancy. Ultrasound examination at admission showed a maximal vertical pocket (MVP) of 11.4 cm in twin A and an MVP of 4.7 cm in twin B. At 33 weeks' gestation, the MVPs had increased to 22.2 cm and 10.2 cm, respectively. At 33 weeks and 2 days' gestation, Cesarean section was performed because of uncontrolled uterine contractions associated with polyhydramnios. Twin A was a female weighing 2,280 g, and twin B was a female weighing 1,782 g (22% growth discordance). The estimated amniotic fluid volumes of twins A and B were 5,000 and 1,000 mL, respectively.