A hemangiosarcoma in a 30 kg, 6-year-old German Shepherd dog showing signs of abdominal distension, anorexia and depression was diagnosed with clinicopathologic examination, abdominal radiographs and ultrasonographic assessmint. In abdominal radiographs, overall abdominal distension was seen. Stomach and some parts of small intestines were deviated caudo-ventrally by enlarged liver. The splenomegaly was also identified and descending colon was dislocated laterally by splenic mass. In ultrasonographic findings, abdominal fluid was identified. Hepatomegaly was seen and it was consisted of multiple, anechoic cysts. The spleen was enlarged and a large round mass with mixed echo pattern at the mid to tail portion of spleen was identified. Grossly, at necropsy, multi-sized cysts in which contained blood and fibrpus materials and some blood were seen in the cross section and it showed hard consistency. Also, lots of small red tumor nodules were dispersed on the serosal surface of the bladder, omentum, mesentery, diaphragm and peritoneum. In abdominal paracentesis, fluid having almost the same properties as circulating blood was identified. The hemoperitoneum was thought to be resulted from the bleeding into peritoneum owing to the rupture of cystic lesions located on the superficial liver area.