The present article reports a case of multicentric hemangiosarcoma in a 22-year-old Warmblood mare presented for recurrent fever and weight loss. Thoracic ultrasonography showed multiple small areas of pulmonary consolidation. Ultrasonography in the region of the right liver lobe showed the presence of a rounded mass, approximately 24 × 19 cm 2 in size, extending from the 9th to 14th rib of the right side, characterized by multiple fluid-filled cavities and hypo- and hyperechoic rounded areas. On the left side, several hyperechoic rounded areas were detected in the spleen. Because of sudden onset of hemoperitoneum and worsening of the clinical conditions, the mare was humanely destroyed. Necroscopy confirmed the presence of hepatic, splenic, and pulmonary lesions, and showed further nodules on the stomach wall. The microscopic appearance of the lesions was consistent with hemangiosarcoma with multiple visceral metastases. Because the reported prevalence of equine hemangiosarcoma is as low as 0% to 0.7%, this case report may provide further information and describe one of the possible ultrasonographic patterns of multicentric hemangiosarcoma in horses.