This investigation was carried out to study the gene action in pea (Pisum sativum L.) under normal and heat stress conditions at the experimental farm faculty of Agriculture, South Valley University, Qena, Egypt, during the two seasons (2021-2022) and (2022- 2023), respectively. The results showed that the mean squares of 45 genotypes were highly significant for all studied traits, reflecting a tremendous wide genetic variability among them. The analysis revealed highly substantial additive and non-additive effects over normal and heat stress conditions, as indicated by the significance of (a) and (b) items. The additive mean square was more significant than the non-additive for all the studied traits under both environmental conditions. Additive genetic variance (D) and Non-additive (H1 and H2) components were highly significant for all traits under normal and heat stress conditions. The values of heritability in broad senses and narrow senses were estimated for all studied. The results of narrow sense (h2 ) heritability h2 value was higher than 50% for most traits except fresh pod yield/plant. Finally, it could be concluded that the additive and non- additive gene action played a major role in controlling for all traits under normal and heat stress conditions, and useful for breeding and selection programs. Also, it is possible to predict the existence of super genetic isolation in future generations.