Abstarct: In order to investigate the effect of foliar application of zinc nanoparticles on some growth traits and yield of three sorghum (Sorghum bicolor L.) cultivars under water deficit condition, an experiment was performed at the research farm of Shahrood University of Technology in the growing season of 2018-19. The experiment was arranged as split plot factorial baxsed on randomized complete block design with three replications. Water deficit stress treatment in two levels of 10 and 20 days irrigation interval were assigned as main plots and sub plots were the combination of the two factors: sorghum cultivars at three levels: Aresk, Speedfeed and Pegah, and foliar application of zinc in three levels of control, micro and nano-particles forms at concentration of 2 gr.l.-1.The results showed that by increasing the irrigation interval from 10 to 20 days, plant height, stem diameter, leaf area index, chlorophyll a, chlorophyll b, carotenoids, relative leaf water content, proline, grain protein, zinc content, wet and dry forage yield and grain yield decreased significantly. However, application of zinc in nano or conventional form causes a significant increase in height, stem diameter, leaf area index, chlorophyll a, chlorophyll b, carotenoids, relative leaf water content, proline, protein, zinc content, wet and dry forage yield and grain yield under stress conditions. The highest fresh and dry forage yield and grain yield were observed at the rate of 97.4, 18.8 and 8.49 ton.ha-1 respectively in irrigation interval of 10 days treatment. Results showed in the most of growth traits, grain and forage yield the local Arsek cultivar was better significantly than Speed Feed and Pegah cultivars at stress and non-stress condition. baxsed on the results of this experiment the use of zinc in nano or normal form in sorghum nutrition programs can improve the growth and yield of quantitative and qualitative of sorghum and reduce the harmful effects of water deficit stress.