Malignant tumors arising from venous walls in the lower extremities are uncommon and intravascular leiomyosarcoma represents only a small proportion and rare of soft tissue leiomyosarcoma. All publications in the literature are of small clinical series or case reports. We present a case of primary leiomyosarcoma of the femoral vein in a 40 year old man; which is a rare lesion with less than 40 cases reported. The patient presented with swelling and localized leg pain. The diagnosis was made histopathologically, the tumor was resected, vascular reconstruction was performed, and for postoperative radiation therapy and chemotherapy patient was referred to the oncologist. Primary leiomyosarcoma of a major peripheral artery is extremely rare, and this report share the clinical presentation, histopathological findings, treatment, and prognosis in these patients.