Background: Retroperitoneal leiomyosarcoma, a malignant neoplasm with smooth muscle differentiation, seldom metastasize. The gastrointestinal tract is rare site of metastases, and diffuse polypoidal involvement is an uncommon presentation. Case Report: A 61-year-old male diagnosed with retroperitoneal leiomyosarcoma underwent surgical resection of the tumor along with chemotherapy and radiation. He presented with 2 months history of vomiting, and melena. Upper gastrointestinal (GI) endoscopy, capsule endoscopy and colonoscopy revealed numerous polypoidal lesions throughout the gastrointestinal tract, suspicious of a GI polyposis syndrome. Histopathology, including immunohistochemistry, confirmed metastatic leiomyosarcoma. Conclusion: Diffuse polypoidal lesions in the gastrointestinal tract presenting as metastases from a retroperitoneal leiomyosarcoma are extremely rare.