Partial molar pregnancy is a rare entity in which there is usually a triploid abnormal fetus associated with a large placenta with cystic changes. The incidence of a normal diploid fetus and a partial molar placenta is extremely rare. Here we report a case of partial molar pregnancy in which a normal appearing male fetus with diploid karyotype coexist. Afocal placental abnormal region was detected at 11 week of gestation as enlargement associated with cystic changes. Fetus shoawed no obvious abnormality. The patient underwent amniocentesis and the result was compatible with a normal diploid male fetus. Regarding these findings the patient continued her pregnancy under close observation and advanced sonographic evaluations were made to rule out other differentials.There were no obstetric complications until the 26th gestational week when preterm rupture of the membranes occurred. The patient underwent induced vaginal delivery and the products were sent for pathologic evaluation which confirmed the partial molar changes