To identify the antidiabetic plants of Iran, a systematic review of the published literature on the efficacy of Iranian medicinal plant for glucose control in patients with type 2 diabetes mellitus was conducted. We performed an electronic literature search of MEDLINE, Science Direct, Scopus, Proquest, Ebsco, Googlescholar, SID, Cochrane Library Database, from 1966 up to June 2010. The search terms were complementary and alternative medicine (CAM), diabetes mellitus, plant (herb), Iran, patient, glycemic control, clinical trial, RCT, natural or herbal medicine, hypoglycemic plants, and individual herb names from popular sources, or combination of these key words. Available Randomized Controlled Trials (RCT) published in English or Persian language examined effects of an herb (limited to Iran) on glycemic indexes in type 2 diabetic patients were included. Among all of the articles identified in the initial database search, 23 trials were RCT, examining herbs as potential therapy for type 2 diabetes mellitus. The key outcome for antidiabetic effect was changes in blood glucose or HbA(1) c, as well as improves in insulin sensitivity or resistance. Available data suggest that several antidiabetic plants of Iran need further study. Among the RCT studies, the best evidence in glycemic control was found in Citrullus colocynthus, Ipomoea betatas, Silybum marianum and Trigonella foenum graecum.