This investigation was carried out to evaluate heterosis, combining ability, gene action and heritability of yield component traits for three commercial cotton varieties G90, G85 and G92 as female and three genotypes as male (G83x “G75x5844"), (G77xG70) and (G89xPima S6) using line x tester analysis. Results indicated that mean squares due to all 15 genotypes including parents and crosses were highly significant for all studied traits indicating the presence of sufficient genetic variability in this population. It was also found that parents vs. crosses mean squares as expressed to average heterosis over all crosses were highly significant for lint percentage and seed index. The mean performance of parents and their F1's hybrids gave a wide range of variation for all studied traits. Heterotic values over the mid- and the better-parent varied between positive or negative significance and highly significant for most of the studied traits. The estimates of variance due to SCA were positive and higher in magnitude than the variance of GCA for all studied traits indicating that the non-additive genetic effect played a major role in the genetic expression of these traits. While, additive effects had a minor role in the inheritance of these traits indicating that the hybridization program would be effective in improving yield and its components traits. Comparing the GCA effects of individual parent revealed that G83xG75x5844 was the best combiner for all studied traits. Dominance estimates were higher than the additive estimates for all studied traits indicating more importance for dominant gene effect in the inheritance of these traits. Estimates of heritability in both broad and narrow senses for yield and its components showed high heritability values in broad sense were detected for all traits under investigation.