We examined the effect of Bulnesia sarmienti (BS) water extract on hyperlipidemia induced by a high-fat diet. ICR mice were fed a high-fat diet ad libitum for four weeks. Simultaneously, BS water extract was administered intragastrically at 0 mg/kg (control), 30 mg/kg, or 300 mg/kg once daily for four weeks. Male ICR mice were divided into four groups; normal control group (NC), high-fat diet+vehicle treatment group (HF), high-fat diet+BS of 30 mg/kg treatment group (HF+BS30), and high-fat diet+BS of 300 mg/kg treatment group (HF+BS300). The levels of serum biochemical parameters and histological appearances were evaluated. After four weeks, body weight gain and serum levels of triglycerides, total cholesterol, and Low-density lipoprotein (LDL)-cholesterol were significantly higher in the HF group than in the normal control group. Together, serum High-density lipoprotein (HDL)-cholesterol level in the HF group was lower than that in the normal control group. However, treatment with BS resulted in significantly reduced body weight gain and levels of serum triglycerides, total cholesterol, and LDL-choleterol. In addition, serum HDL-cholesterol level in the BS treatment group was significantly elevated, compared to that of the HF group. Histopathological evaluation of the liver showed fat accumulation and swelling of hepatocytes in the high-fat diet group; these abnormalities were ameliorated by treatment with BS. These results suggest that treatment with BS water extract resulted in dose-dependent prevention and mitigation of high-fat diet-induced hyperlipidemia.