Aims The aim of present study was to investigate the effects of isosteviol on hyperglycemia and hyperlipidemia in rats fed with high-fat emulsion (HFE). Main methods Hyperglycemia and hyperlipidemia in rats was induced by daily ingestion of HFE for 14 days. Isosteviol (0.2, 1.0, or 5.0 mg/kg/day) was orally administered for 7 days, with rosiglitazone maleate (5.0 mg/kg/day) used as the positive control. The levels of fasting serum glucose (FSG), fasting serum insulin (FSI), total cholesterol (TC), triglyceride (TG), high density lipoprotein (HDL), and low density lipoprotein (LDL) in serum were assayed. Intravenous glucose tolerance test (IVGTT) was performed with serum glucose and insulin levels monitored. The effect of the supplement of palmitate in HFE on the activity of isosteviol was investigated. Ultrastructural changes in islet ߭cells and peroxisome proliferator-activated receptor a (PPARa) mRNA expression profile were determined. Key findings FSG, FSI, TC and LDL levels and insulin resistance index (IRI) were decreased and HDL level was increased by all doses of isosteviol. During IVGTT, serum glucose levels were decreased by isosteviol and no significant differences were observed in insulin release between isosteviol-treated and control groups. The effects of isosteviol were attenuated by palmitate. Damage to pancreatic islet cells was partially attenuated, and expression profile of hepatic PPARa mRNA was enhanced by isosteviol. Significance Antihyperglycemic effects of isosteviol could enhance utilization of glucose in the periphery and reduce ߭cell damage induced by dyslipidemia. Modulating-lipidemic effects of isosteviol might be related to the potential enhancement of liver PPARa mRNA expression.