It is desirable for sorghum breeder to know the extent of relationship between yield and each of morphological and physiological traits affecting it which facilitate breeder in selecting plants of desirable traits, especially under drought stress conditions. Therefore, this work was conducted at two locations represent clay and sandy soils of the Experimental Farms of Faculty of Agriculture, Assiut University, Assiut, Egypt, during two summer seasons 2014 and 2015 under two water regimes. To obtain the well-watered conditions (WW), surface irrigation was applied in the clay soil and genotypes were watered each 14 days, while drip irrigation system was used in the sandy soil and plants were watered for 2 hours each 3 days. To induce drought stress conditions (DS), the third and the fifth surface irrigations were skipped in the clay soil, while plants were drip irrigated for 1 hour each 3 days in sandy soil. Three statistical procedures i.e., simple correlation coefficient, the path coefficient analysis and the stepwise regression analysis were performed to determine the functional relationships between yield and each of its attributes and some physiological traits under both treatments. For this, 43 grain sorghum genotypes including 30 F1 hybrids, their elven parents (6 female and 5 male lines were crossed in line x tester mating fashion) and two check cultivars were used in this study. Results revealed highly significant differences among genotypes for all studied traits under WW and DS conditions. Panicle weight had the highest positive correlation with grain yield of sorghum genotypes under both treatments followed by threshing percentage and seed index, reflecting these traits are the most contributed to yield. Path analysis showed that panicle weight and threshing percentage had positive and direct effect on grain yield/plant, while chlorophyll content, excised leaf water loss and stay green were the most important physiological traits under DS conditions. In addition, panicle width and chlorophyll content showed the highest positive indirect effects on grain yield. Stepwise regression exhibited that panicle weight and threshing percentage had the strongest variation in grain yield per plant under both water regimes. On the other hand, all physiological traits except excised leaf water loss (under WW conditions) showed positive correlation coefficient with GY/P under both treatments. Stepwise regression revealed that relative water content was the most important physiological trait followed by flag leaf area under WW conditions, while chlorophyll content was the most important physiological trait under DS followed by excised leaf water loss that contributed high amount of the total variation of grain yield.