The prevalence of umbilical cord cysts at 7-13 weeks' gestation is approximately 3%. More than 20% of such cases are complicated by structural defects and/or chromosomal abnormalities such as trisomy 18. These cysts usually have a single cavity and are <5 cm in size. Therefore, when an umbilical cord cyst is detected in the 2nd trimester, the examination of fetal karyotype is recommended. Omphaloceles are also well known to be complicated by many anomalies, especially trisomy 18. We report a case of an omphalocele associated with a large multilobular umbilical pseudocyst (diameter >5 cm) in a patient with a normal karyotype, 46XY. These anomalies were diagnosed by fetal ultrasonography. However, the cyst was difficult to diagnose as an umbilical cord pseudocyst because it was very large and multilobulated. At 38.5 weeks of gestation, the patient was delivered by Cesarean section. The cyst was resected, and the omphalocele was closed by staged surgeries. Pathologic diagnosis of the cyst was the degeneration of Wharton's jelly. This diagnosis was made by the absence of epithelial lining inside the cyst wall, since the existence of epithelial cells correlates with true cysts.