This study aimed to analyze the ameliorative effect of Crataegus aronia against type 2 diabetes mellitus (type 2-DM). Type 2-DM rats were treated with the extract and the changes in serum parameters (glucose, insulin, HbA1c and lipids) and hepatic parameters (oxidative stress, inflammation and mRNA levels of GLUT-2 and gluconeogenesis enzymes) were compared to those of control and untreated type 2-DM rats. Also, levels of hepatic insulin receptors 1A (IR-1A) were measured immunohistochemically and compared between groups. In type 2-DM rats, C. aronia significantly improved the oral glucose tolerance test (OGTT), lowered plasma glucose, serum lipid levels and the hepatic glycogen content. Also, it significantly lowered the levels of hepatic lipid peroxidation, tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) and enhanced the level of reduced glutathione (GSH) and increased superoxide dismutase (SOD) activity. C. aronia enhanced hepatic mRNA expression of the insulin receptor A isoform (IR-A) and glucose 6-phosphatase (G6Pase), and lowered glucose transporter-2 (GLUT-2) and glycerol kinase (GK) mRNA expression. In conclusion, C. aronia ameliorates T2DM by inhibiting hepatic glucose output.