Elevated carbon dioxide concentrations in the atmosphere may increase water-use efficiency in crops and mitigate yield losses brought about by climate change. On the other hand, water scarcity is the main limiting factor in the world. Therefore, under these conditions, application of nitrogen fertilizers requires proper management. The present study was conducted to investigate the physiological, biochemical and growth responses of two millet cultivars (Bastan and Pishahang) to different irrigation regimes (40% MAD "control", 75% MAD "drought stress") and nitrogen nutrition levels (0 and 85 mg kg -1 , nitrogen from Urea fertilizer, N= 45%) as afactorial experiment arrangedin acompletely randomized design with three replications under two separate environments (ambient (390±50) and elevated air carbon dioxide concentrations (700±50 µmol mol -1 ) in 2016 at IUT University, Iran. Compared to the ambient CO 2 concentration, elevated levels increased the concentrations of chlorophyll a (Chla), chlorophyll b (Chlb) and carotenoids (Car), membrane stability index (MSI), leaf relative water content (RWC), leaf area, plant height, root volume, root and shoot dry weights, shoot NUE and root nitrogen concentration, but decreased activity of antioxidant enzymes such as catalase (CAT), peroxidase (POD) and ascorbate peroxidase (APX), proline concentration, malondialdehyde (MDA) content, hydrogen peroxide concentration (H 2 O 2 ), shoot nitrogen concentration and root NUE. Water deficit, compared to control, increased activity of antioxidant enzymes such as CAT, POD and APX, proline, MDA and H 2 O 2 concentration, nitrogen concentration of shoot and root, but decreased Chla, Chlb and Car, MSI, RWC, leaf area, plant height, root volume, root and shoot dry weights, shoot and root NUE. Bastan indicated higher Chla, Chlb, Car, CAT activity, APX activity, MSI, RWC, plant height, H 2 O 2 concentration and nitrogen concentration of shoot and root relative to Pishahang cultivar. While, Pishahang showed a greater POD activity, proline concentration, MDA content, leaf area, shoot dry weight, root dry weight, root volume and NUE of shoot and root compared to Bastan cultivar. Elevated CO 2 under normal irrigation and water deficit levels, respectively, increased chlorophyll a (by 39 and 27%), chlorophyll b (by 43 and 24%), leaf relative water content (by 6% and 15%), leaf area (by 43% and 10%), and root dry weight (by 47% and 35%) but decreased the activity of catalase (by 35 and 17%), ascorbate peroxidase (by 25% and 30%), and the concentration of hydrogen peroxide (by 3% and 24%). N supplement affected the measured traits more notably under elevated level ccompared to the ambient CO 2 level. N supplement increased chlorophyll a by 27% and 38%, chlorophyll b by 17% and 31% and leaf area by 16% and 43% of the presence of 390 and 700 µmol mol -1 CO 2 , respectively. N supplement resulted in increases of 34% and 31% in chlorophyll a, 30% and 18% in chlorophyll b, 46% and 11% in leaf area and 27% and 15% in shoot dry weight and decreases of 8% and 5% in RWC and 2% and 29% in MDA at the presence of control and drought, respectively. There was significant difference in activityof antioxidant enzymes of the two millet cultivars in terms of their response to elevated CO 2 and increasing CO 2 concentration reduced the antioxidative activity of catalase and ascorbate peroxidase in Bastan more notably than Bishahang cultivar. The results showed that elevated CO 2 and N supplement may ameliorate the destructive effects of water deficit stress on the growth and physiological attributes of millet. Keywords: Antioxidant enzymes, Carbon dioxide, Climate change, Drought stress, Nitrogen supply.