This study was designed to evaluate antihyperglycemic and antihyperlipidemic effects of ethanol extracts of Taraxacum mongolicum (T.m.) on streptozotocin (STZ)-induced diabetic rats. Sprague-Dawley rats were randomly assigned to five groups: normal (NC), STZ-control (DC), and three experimental groups. Diabetes was induced in Sprague-Dawley rats with a single intravenous injection [45 mg/kg body weight (b.w.)] of STZ. An ethanol extract of T.m. was orally given to diabetic rats for 14 days. Three experimental groups were additionally treated with T.m. extract at doses of 1 g/kg b.w./day for T.m.-1, 2 g/kg b.w./day for T.m.-2, and 3 g/kg b.w./day for T.m.-3. Oral administration of T.m.-2 significantly increased their body weights. T.m.-1 and T.m.-2 significantly decreased aspartate aminotransferase (AST) levels than DC. T.m.-1 and T.m.-2 group significantly decreased blood glucose levels. Total cholesterol, triglycerides, and free fatty acids were significantly decreased whereas high-density lipoprotein cholesterol was significantly increased in groups treated with T.m. extract than those in the DC group. These results support the fact that administration of T.m. extract can reduce hyperglycemia and hyperlipidemia risk in diabetic rats.