Background: The metabolic syndrome is associated with increased risks of cardiovascular diseases and diabetes mellitus. Objectives: As alternative medicine emerged worldwide, this study aimed to evaluate the efficacy of Berberis vulgaris (barberry fruit) in the treatment of metabolic syndrome. Methods: This is a Randomized, placebo controlled, double-blind, Trial with two treatment arms. A total of 60 patients with metabolic syndrome were Randomly assigned to receive barberry or placebo tablets (one 550 mg tablets per day for 3 weeks). Total cholesterol, LDL, HDL, triglyceride, fasting blood sugar and hematocrit were measured before and after 21 days of treatment. Data were analyzed using Mann-Whitney U and paired t-test by SPSS (V. 15) software. P-values < 0. 05 were considered to be significant. Results: In the barberry group, there was a significant decrease in systolic blood pressure (pre-treatment 123. 1 13. 1 vs. posttreatment 117. 7 13. 2, P-value = 0. 04), waist circumference (pre-treatment 105. 9 7. 5 vs. post-treatment105 7. 7, P-value = 0. 04) and hematocrit (pre-treatment 45 3. 6 vs. post-treatment 43. 5 2. 7, P-value = 0. 004) but other parameters did not change significantly. Serum cholesterol was significantly reduced after intervention in the barberry group (-17 61. 1 vs. 23. 6 45, P-value = 0. 02). Conclusions: We observed a significant effect of barberry on systolic blood pressure and waist circumference. Further studies with larger samples are needed to longitudinally investigate the effect of metabolic syndrome.