We investigated the antioxidant defense mechanism, metal uptake and lipid peroxidation (LPO) levels at different leaf positions in Mentha piperita L. grown in Mn2+-deficient and control conditions. Under manganese deficiency the activity of superoxide dismutase (SOD), catalase (CAT) and guaiacol peroxidase (GuaPOX) and the content of ascorbate, chlorophyll, and carotenoid under Mn2+ deficiency were significantly lower than in the control for all leaf positions. SOD activity correlated positively with Mn2+ uptake. Fe2+ uptake was inhibited by Mn2+ deficiency. During early stages of Mn2+ deficiency, M. piperita leaves showed relatively more antioxidant activity and lower LPO. Towards the final stages of the treatment period, comparatively lower SOD, CAT and GuaPOX activity and higher LPO levels accelerated the senescence process.