Pennyroyal (Mentha pulegium L.) from the Lamiaceae family is a medicinal plant which has great antioxidant properties. Environmental stresses such as drought can result in changes in the activity of antioxidant enzymes and the content of some biochemical factors in plants. In this investigation, the effects of drought stress on the activity of superoxide dismutase, ascorbate peroxidase, catalase, peroxidase, malondialdehyde and soluble sugars content in pennyroyalshoots and roots were evaluated. To create the water deficit, 24-day seedlings of pennyroyal were placed in 1.2 strengthHoagland solution, containing PEG 6000 (0 and 5% (w/v)) for 24 hours. The results showed that drought stress increased catalase activity and lipid peroxidation and decreased superoxide dismutase and peroxidase activity of the shoots.On the other hand, the activity of catalase and peroxidase increased in the roots. Ascorbate peroxidase activity showed no signify cant difference in the shoots and the roots. Moreover, drought stress significantly increased the amount of solublesugars of glucose, galactose, xylose and rhamnosus in the shoots. Therefore, the increased activity in antioxidantenzymes as well as the amount of soluble sugars under drought stress might be a sign of tolerance of M. pulegium underlow levels of drought.