Abstract: A diallel cross comprising eight inbred lines of maize was evaluated to determine the genetic trend of maize inbred lines across two different planting conditions (normal and water stress). Grain yield and its related traits revealed highly significant differences among inbred lines under both plantings. Graphical analysis revealed that additive gene action for plant height under normal condition remained unchanged under water stress while over-dominance type of gene action for leaf area per plant, 1000-grain weight and grain yield per plant under normal experiment also remained unchanged under water stress. It was revealed that over-dominance type of gene action for biological yield under normal changed to additive with partial type of gene action under moisture stress condition whereas, additive type of gene action for harvest index under normal changed to over-dominance type of gene action under water stress.