Background and Objective: Adiponectin is a novel adipose tissue-specific adipokine that can increase insulin sensitivity. Many studies have shown anti obesity and anti diabetic effects of green tea consumption. In this study we examined the effects of green tea extract on circulating adiponectin levels and insulin resistance status in patients with type 2 diabetes mellitus (T2DM). Materials and Methods: In this double blind randomized clinical trial 58 type 2 diabetic patients with BMI ≥ 25 were recruited from an unselected population from the outpatient clinic of Shariati Hospital, Tehran, Iran. Patients were randomly divided into two groups green tea extract and placebo. All the patients received the capsules for 8 weeks. Laboratory measurements including fasting serum adiponectin, insulin, HOMA-IR, FPG, OGTT, HbA1c and lipid profile and anthropometric were performed before and after the intervention. Nutrient intakes were obtained via 24- hour recall from each patient in three successive days. The data were analyzed using appropriate software. Results: We found a significant effect of green tea extract on increasing the logarithm of serum adiponectin in diabetic patients (0.15±0.10 µg/ ml, P < 0.05). A significant independent correlation between the logarithm of serum adiponectin and WHR (Waist to Hip Ratio) was found (P= 0.009, t= -2.7). The consumption of green tea extract had a significant effect in control the levels of HbA1C, weigh and also BMI in green tea group (P < 0.05). Conclusion: The results showed that consumption of green tea extract can be useful in the control of T2DM by increasing the levels of serum adiponectin and controlling the weight, BMI and HbA1C levels in patients with T2DM.