The present study was carried out at Gemmeiza Agricultural Research Station, El-Gharbia Governorate, Egypt, during the three growing seasons of 2019/20, 2020/21, and 2021/22 to determine the genetic variance components and type of gene action controlling yield and its components by using the means of the six populations (P1, P2, F1, F2, BC1, and BC2) of the four barley crosses. The base generation of the four crosses was sown under normal (1636.06 m3 fed^-1) and water stress conditions (601.06 m3 fed^-1). Mean effects (m) varied for all attributes in all crosses and were highly significant. Additionally, under both scenarios, the relative significance of additive-dominance effects changed with characters and crosses. Results generally showed that non-allelic interactions existed in all crosses for all the examined characteristics. In most of the examined traits, dominance was stronger than additive and additive dominance among the epistatic components, showing that these traits were significantly influenced by dominance and associated non-allelic interactions. For the majority of the examined qualities under both circumstances, positive heterotic effects compared to the mid parent and better parent were discovered. For the majority of the studied traits, the highest predicted genetic advance values were paired with high and moderate narrow-sense heritability values in all crosses. These findings suggested that early generations could be used for selection to obtain high-yielding genotypes under either normal or stressful conditions. Finally, the most promising crosses were the two crosses 2 and 3 under water stress conditions (601.06 m3fed-1), which had high genetic advances associated with high heritability and would be of interest in breeding programs for improving the most studied traits in barley.