Twin anemia polycythemia sequence (TAPS) is a form of twin-to-twin transfusion syndrome that occurs very rarely and may not be diagnosed until after delivery. The condition leads to increased risk of perinatal morbidity and mortality. We present two cases of monochorionic diamniotic twins, in which the diagnosis of TAPS was made after documenting a discrepancy in the echodensities of the two portions of the placenta. Postnatal hemoglobin differences between the twins confirmed the diagnosis of TAPS. On the basis of these two cases, it appears that the heterogeneity in placental echogenicity is a sign of TAPS and Doppler measurement of middle cerebral artery peak systolic velocity is helpful for early diagnosis and management with timely delivery.