We studied the effects of fish oil and wakame diets given to rats on the liver concentrations and fecal bile acid excretion. Young male rats were fed a diet containing the control, wakame, fish oil or fish oil + wakame for 4 weeks. The control diet contained a soybean oil. Fats of the testes around and epididymal fat pad weights decreased in the wakame group, fish oil group and fish oil + wakame group compared to the control group. It seemed that the effect was the highest in the fish oil + wakame group. The concentrations of the total cholesterol and triglyceride in the liver decreased in the wakame group, fish oil group and fish oil + wakame group compared to the control group. For the group fed with wakame, the concentration of liver lipids appeared to decrease. The bile acid excretion of feces was significantly increased in the fish oil + wakame group compared to the other groups. It was clarified that the bile acid excretion of feces increased by the fish oil + wakame diet rather than only wakame. These results suggested that the group fed the fish oil + wakame diet had a decreased fat accumulation, and increased fecal excretion of bile acids, which was expected to prevent metabolic syndrome and cardiovascular disease.