A flowerhorn fish with a subopercular mass, which had been reared in one of the private commercial aquaria was sent to the laboratory just before death. This fish began to show symptoms such as lethargy, anorexia, depression and dyspnea, and eventually died. The mass and intestinal organs were examined histopathologically. Thyroid showed variably sized follicles that contained abundant colloid and liver revealed steatosis. This report presents a case of goiter in the flowerhorn cichlid and its effect on the liver.