Twenty F1 grain sorghum crosses, their parents (five CMS A-lines and four male R-lines) and one commercial hybrid (H-305) as a check were evaluated for grain yield/plant and some other traits in 2017 and 2018 seasons at Shandaweel Agric. Res. Station, Sohag, Egypt under two irrigation levels (100% and 40% from optimum water irrigation level). The combined analysis of variance across two years showed significant or highly significant differences between years, irrigations and genotypes for all the studied traits, indicating genetic variability for all the studied traits. However, the interaction between years × irrigations showed significant mean squares for 1000-grain weight and grain yield per plant. While, mean squares due to the interactions between years × genotypes and irrigations × genotypes were highly significant for all the studied traits, except panicle length, reflecting the differential response of genotypes under conditions of drought stress. Also, the interactions mean squares between years × irrigations × genotypes were highly significant for 1000 grain weight and grain yield per plant. Highly significantly differences were found among genotypes, crosses, and parents for the entire studied traits in 2018 and 2019 seasons. Similarly, highly significant mean squares were obtained for crosses vs. parents for all the studied traits in the two seasons, reflecting the presence of heterosis for all the studied traits. Partitioning sum of squares of crosses into their contributors (females, males and females x males interaction) showed highly significant variances for all the studied traits in 2018 and 2019 seasons. These results reflect that both additive and non-additive gene effects were important in the inheritance of all studied traits and that additive gene effect played the major rule for inheritance of most studied traits. Mean number of days to 50% flowering of the hybrids and their parents were increased by increasing water stress, but plant height, panicle length, 1000 grain weight and grain yield per plant of the hybrids and their parents were decreased. Moreover, the F1 hybrids had taller plants and higher grain yield per plant than the best parent under the two irrigation levels. The female line A-SH-9 and the male line ICSR93001 were good combiners for grain yield per plant. Moreover, some crosses had positive and highly significant SCA effects under two levels of irrigation for 1000 grain weight and grain yield per plant.