Cocoa, the fruit of Theobroma cacao plant is traditionally used in the folk medicine as a pharmaceutical for blood pressure reduction and cardiovascular diseases prevention. The nuclear receptor peroxisome proliferator-activated receptor gamma (PPAR-γ) is widely known to improve insulin sensitivity and is thereby being used as a major drug target for the treatment of type 2 diabetes mellitus. The present study investigated the anti-diabetic/anti-obesity effects of cocoa polyphenol-rich extract (CoPE) using obese-diabetic rats (Sprague Dawley rats). Sprague Dawley rats received either normal diet, high-fat diet or high-fat diet with additional cocoa polyphenols for 8 weeks. After the end of the treatment, body weight, plasma glucose and insulin were measured. Furthermore, mRNA and protein levels of PPARγ were measured in skeletal muscle and white adipose tissue. Compared to the high-fat diet group, increases in body weight, plasma glucose and insulin were significantly suppressed for CoPE-treated groups. Furthermore, compared to the high-fat diet group, the PPARγ mRNA level was significantly higher in both skeletal muscle and white adipose tissue for CoPE groups. Protein expression of PPARγ in CoPE groups was also significantly higher compared to the high-fat diet group. In conclusion, the anti-diabetic mechanism of actions of CoPE along with metformin hypoglycemic drug is partially attributed to increase expression of PPARγ in skeletal muscle and adipose tissue. These results suggest that CoPE could be a useful phytomedicine agent for alleviating insulin resistance.