Hemangiosarcoma is a highly malignant tumor of vascular endothelium or bone marrow origin, often metastasizing to the lungs, liver, and omentum. The purpose of this report was to provide insight into the diagnosis and management of primary renal hemangiosarcoma in a dog, a rare neoplasm with limited documentation. A 10-year-old, spayed female Pomeranian dog, referred for evaluation of a right renal mass incidentally detected without any clinical symptoms, was examined. Ultrasonography and computed tomography revealed a right renal mass compressing the caudal vena cava, with pulmonary metastases, but no other metastatic sites were noted. Due to severe vascular adhesions, nephrectomy was performed with ligation, leaving a small remnant near the vena cava. Histopathology and immunohistochemistry of the mass confirmed renal hemangiosarcoma. Postoperatively, adjuvant chemotherapy with doxorubicin was administered, and the dog survived for 232 days following surgery. This case highlights the importance of a careful surgical approach to manage renal hemangiosarcoma with extensive vascular adhesions and the potential benefit of combining surgery with chemotherapy in achieving extended survival, even in the presence of metastasis.