Herbal preparations have attracted attention in the management of metabolic syndrome. Since time immemorial, medicinal plants have been used in virtually all cultures. The traditional herbs require scientific and medical evaluation. Ten classic herbs have been combined in Dia-No, a polyherbal preparation containing water extracts of its ingredients, known for their anti-hyperglycemic and antihyperlipidemic potential. Efficacy of Dia-No on clinical and biochemical parameters of metabolic syndrome was evaluated. Two hundred patients with metabolic syndrome were selected randomly after meeting inclusion and exclusion criteria. The patients were divided into two groups, one group receiving the drug and the other receiving a placebo bearing a distinctive code number. Anthropometric parameters, metabolic profile fasting blood sugar, HbA1c and lipid profiles were performed initially and after 3 months of treatment. Renal, liver function and any untoward effects were noted.