The serum and liver lipid-lowering effects of dietary freeze-dried blueberry leaf powder (BL) and its hydrothermal extract (BLHE) were examined in rats fed diets with or without cholesterol supplementation. Administration of 1% and 3% BL had no adverse effects on food intake or growth; however, relative liver weights were reduced in rats fed diets with and without dietary cholesterol. In the absence of dietary cholesterol, a dose-dependent reduction was evident. The effects of dietary BL on the concentration of serum lipids were marginal; however, the effects on liver triacylglycerol (TG) and cholesterol levels were apparently dose-dependent when the animals were fed diets free of cholesterol. Further, BL significantly attenuated dietary cholesterol-dependent accumulation of hepatic cholesterol, but not of TG. Hydrothermal treatment studies suggested that the active component of BL in terms of its liver lipid-lowering activity is relatively stable at high temperatures. Histopathological analysis of hepatic tissues revealed that BL administration suppresses fatty infiltrations induced by an AIN 76-based high-sucrose diet. The results of this study suggest that some of the active components of BL extracts, which are incorporated into the liver, prevent fatty liver in rats. These results provide further support for the investigation of dietary BL and derivatives thereof as functional human foods.