The aim of this study is to examine the effect of cabergoline added to metformin on glycemic control, insulin resistance and B-cell function in obese type 2 diabetic patients. Forty obese patients with newly diagnosed type2 diabetes were enrolled in this study and randomized by 1:1 ratio into group (I) receives metformin and group (II) receives metformin plus cabergoline for 12 week. We evaluated fasting plasma glucose (FPG) and postprandial plasma glucose (PPG) every 4 week while body weight, glycosylated hemoglobin, fasting plasma insulin, homeostasis model assessment of insulin resistance (HOMA-IR) and B-cell function (HOMA-B) at the baseline and after 12 week. At the end of the study, Cabergoline plus metformin significantly improved FPG, PPG and HOMA-IR more than metformin alone. Beta-cell functions significantly improved by cabergoline plus metformin but not by metformin alone after 12 week compared with baseline. We can conclude that cabergoline added to metformin improved glycemic control and insulin resistance better than metformin alone.