Hemangiopericytoma is an uncommon mesenchymal neoplasm that may occur anywhere in the body but is most commonin the lower extremities and retroperitoneum. Radiologically, the tumor is mainly a solid hypervascular mass, andwhen large, has some cystic and necrotic portions. It can compress or displace adjacent tissue and organs, and maycause related symptoms. The authors encountered a case of hemangiopericytoma of the popliteal fossa as amultichambered cystic mass containing various-staged hemorrhagic fluid, and report this case together with its MRimaging findings.