Abstarct: This experiment aimed to investigate the effects of magnesium oxide (in two nano and conventional forms) and mycorrhiza under drought conditions on the growth, yield, and morphophysiological traits of sesame in two crop years 2022 and 2023 as a factorial and randomized complete block design with three replications at the research farm of the Faculty of Agriculture, Gonbad Kavoos University. The experimental treatments included two irrigation levels (8 and 16 days as regular irrigation and under-irrigation treatment as the first factor and foliar spraying of magnesium oxide at zero concentrations (control), 0.2% nano magnesium oxide and 0.2% regular magnesium oxide as the second factor and mycorrhizal fungi: no inoculation (control), Funneliformis mosseae and Rhizophagus irregularis as the third factor. Irrigation treatments were applied after plant establishment (6-leaf stage) and foliar spraying of magnesium oxide treatments was done at the early flowering stage. The results showed that under-irrigation treatment significantly reduced grain yield, biological yield, plant height, oil percentage, grain protein percentage, leaf magnesium, membrane stability index, chlorophyll a and b levels and also increased carotenoid, anthocyanin, phenolic compounds content, soluble sugars, proline and increased antioxidant enzyme activity (catalase, superoxide dismutase, ascorbate peroxidase, guaiacol peroxidase and polyphenol oxidase). Also, the combination of magnesium nanooxide and mycorrhizal fungus Muscea species showed the highest cell membrane stability in both years (77.31 and 77.43%), the highest leaf magnesium in both years (3.87 and 3.94 mg/g), the highest grain protein percentage (22.53), the highest thousand-grain weight (2.91 g), and the highest grain yield (1120 kg/ha). The highest harvest index under drought conditions was observed with the combination of magnesium nanooxide + mosseae (about 25.08% in the first year). In this experiment, the highest amount of chlorophyll a (10.91 mg/g wet weight), chlorophyll b (3.53 mg/g wet weight), carotenoid (6.17 mg/g wet weight), anthocyanin (74.7 mg/g wet weight), phenolic compounds content (48.73 mg gallic acid equivalent in 100 grams of leaf fresh weight) was related to the conditions of deficit irrigation and the treatment of magnesium oxide nano + mycorrhizal fungus mosseae. The treatment of magnesium oxide nano + mosseae also had the highest water use efficiency (23 kg/m3 water). The highest activity of catalase, peroxidase, superoxide dismutase and polyphenol oxidase enzymes in both normal and deficit irrigation conditions was related to the treatment of magnesium oxide nano + mosseae. The irregularis species was more successful in the percentage of root colonization in sesame plants than the mosseae species. According to the results of correlation analysis, antioxidant enzymes (polyphenol oxidase, superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase) demonstrated a strong correlation with seed yield. Proline exhibited a moderate correlation with seed yield in most environments, whereas root colonization percentage showed a weak correlation with seed yield. baxsed on the biplot analysis, nano-magnesium oxide was found to be suitable for enhancing primary mextabolites and sesame yield, while mycorrhizal fungi increased secondary mextabolism and root colonization in sesame. In general, it can be stated that the combined use of magnesium oxide foliar spraying and mycorrhizal fungus was effective in both normal and deficit irrigation conditions, but the effectiveness of magnesium oxide nano and mosseae fungus in deficit irrigation conditions was greater than that of the Irgiularis species in sesame plants, especially in deficit irrigation conditions.