This investigation was carried out in two separate experiments in a geenhouse at Isfahan University of Technology, Iran in 2013. In the first experiment15 sorghum genotypes were evaluated under two levels of carbon dioxide (380 and 700 µM) and two levels of salinity (0 and 90 mMNaClin nutrient solution). The results showed thatthe responses of all tested sorghum genotypes to elevated CO 2 were positive in terms of dry matter accumulation, but to different extents.The positive effect of elevated CO 2 was low (less than 20% increase in dry matter accumulation) in MGS 5 , medium (between 20 and 40%) in 3, 4, 13, 14, 25, 26, Pegah, Sepideh, MGS 2, KGS 33 and KGS 29 and high (more than 40%) in 28, 24, 5 genotypes. There were considerable differences among sorghum genotypes in response to salinity. The extent of decrease in shoot dry weight due to salinity of 90 mMNaCl was less than 40% in 14, MGS 2 , MGS 5 and KGS 33, between 40 and 60% in 3, Pegah and Sepideh and more than 60% in 4, 5, 13, 24, 25, 26, 28, and KGS 29 genotypes. In the second experiment, four sorghum genotypeswerestudied under two carbon dioxide and salinity levels (the same as the first experiment), using two nitrogen sources (vermicomposte and ammonium nitrate). The results showed that with an increase in salinity level, the concentration of sodium in shoot and roots, the activities of catalase, ascorbate peroxidase and superoxide dismutase, the concentration of proline and soluble carbohydrates were increased but the concentration of potassium in shoot and roots, K/Na ratio in shoot and roots, the concentration and the content of nitrogen in shoot and roots, the concentration of chlorophyll a, chlorophyll b and total chlorophyll in leaves, chlorophyll a/b ratio, the concentration of carotenoids,plant height, root volume, shoot and root dry weight and planttotaldry weight and also shoot/root dry weight were decreased. With an increase in air CO 2 level, the concentration of potassium in shoot and roots, K/Na ratio in shoot and roots, the concentration of nitrogen in roots, nitrogen use efficiency in shoot, the concentration of chlorophyll a, chlorophyll and total chlorophyll in leaves, chlorophyll a/b ratio, the concentration of carotenoids, plant height, root volume, shoot and root dry weight were increased but the concentration of sodium in shoot and roots, the concentration and content of nitrogen in shoot, nitrogen use efficiency in roots, shoot/root nitrogen ratio, the activities of catalase, ascorbate peroxidase, and superoxide dismutase, the concentration of proline and soluble carbohydrates were decreased. In both experiments, the positive effect of elevated CO 2 on shoot dry weight was geater in non-saline than in saline condition.While, the positive effect of elevated CO 2 on root dry weightwas more pronounced under saline condition.The application of vermicomposte as compared to ammonium nitrate increased the concentration of sodium in shoot and roots, nitrogen use efficiencyin shoot and roots, shoot/root nitrogen ratio,chlorophyll a/b ratio, the activities of catalase, ascorbate peroxidase, and superoxide dismutase but decreased the concentration of potassium in shoot and roots, K/Na ratio in shoot and roots, the concentration of nitrogen in shoot and roots, the concentration of chlorophyll a, chlorophyll and total chlorophyll in leaves, the concentration of carotenoids, plant height, root volume, shoot and root dry weight and shoot/root dry weight ratio.The results of this experiment showed that there was considerable variation among sorghum genotypes in response to elevated air CO2 and the positive effects of elevated air CO2 on plant growth were reduced under saline condition. Keywords: Climate change, Salinity Stress, Sorghum genotypes, Elevated CO2, Ammonium nitrate, vermicomposte.