Abstract One potential plant species suggested for phytoremediation of heavy metal contaminated soils in Korea is evening primrose ( Oenothera odorata). In this study, the tolerance mechanism of O. odorata to Cd exposure was investigated using tissue concentration of malondialdehyde (MDA) and growth decline (fresh weight and root elongation) as indicators of Cd induced stress when grown under hydroponic conditions. Compounds containing thiol functional groups including phytochelatins (PCs) were also determined in both root and shoot. In response to elevated Cd concentrations, the growth of O. odorata decreased, and shoot synthesis of MDA increased as the concentration of Cd accumulated in the tissue also increased. Simultaneously, MDA synthesis in the root was suppressed despite much more Cd being accumulated in the roots compared to the shoots. The suppression of MDA synthesis in the roots was related to PCs synthesis since much higher PC concentrations were observed in roots than in shoots. The synthesized PCs resulted in mitigation of Cd activity through complexation and compartmentalization in tissue and consequently Cd induced MDA production was reduced. Therefore, this study clearly demonstrated that PC synthesis has a significant role in the Cd tolerance of O. odorata.