Abstract: Cadmium (Cd) is a non-essential heavy metal that does not have any metabolic use and can be harmful even at low concentrations. Blackgram (Vigna mungo L. Hepper cv. T9) plants were grown in pots containing a mixture of soil and compost treated with 0, 25, 50 and 100 mg Cd kg^-1 soil as CdCl₂ for 30 days. The changes in total Chlorophyll (Chl), Chl a/b, net photosynthetic rate (P_N), stomatal conductance (gs), Water Use Efficiency (WUE) and Carbonic Anhydrase (CA) activity were noted. The activities of antioxidative enzymes in root and leaf were also assayed together with the content of Thiobarbituric Acid Reactive Substances (TBARS) and hydrogen peroxide (H₂O₂). The concentration of Cd in root and leaf increased with the increasing Cd concentrations. Greatest decrease in photosynthetic traits was observed with 100 mg Cd kg^-1 soil. The activity of Superoxide Dismutase (SOD) increased in leaf but decreased in root, whereas the activity of catalase (CAT) decreased in both root and leaf. By contrast to CAT, the activity of ascorbate peroxidase (APX) increased in root and leaf. However, GR activity increased in root and decreased in leaf. The results suggest that the antioxidative enzymes showed differential pattern in root and leaf and the decrease in photosynthesis with 100 mg Cd kg^-1 soil was associated with the accumulation of TBARS and H₂O₂ content and reduction in Chl content, stomatal conductance and CA activity.