Phyllode tumor (PT) is extremely rare tumor of the breast. Distant metastasis occurs in 10-20% of patients with malignant phyllode tumor. The most common sites of metastases are the lungs and bones. Although theoretically any organ may have metastasis, an isolated duodenum metastasis has not been documented as yet in the English-language literature. We report herein a case with a isolated duodenal metastasis from PT of breast in a 31 year-old-woman who underwent right mastectomy 4 years before because of the recurrent malignant PT. She presented to our hospital with massive upper gastrointestinal bleeding. Clinical evaluation revealed a huge mass originated from duodenum. Urgent laparotomy and pancreaticoduodenectomy were carried out in order to remove the bleeding duodenal mass.The pathologic examination of the resected specimen showed a malignant spindle cell tumor consistent with metastatic malignant PT. Our case of gastrointestinal bleeding due to an isolated duodenal metastasis as a result of hematogenous spread from malignant phyllode tumor of breast is unique in the English literature and pancreaticoduodenectomy is a curative treatment for patients with isolated duodenal involvement.