This study was conducted at Sakha Agricultural Research Station, Cotton Research Institute, Agricultural Research Center, Kafr El-Sheikh Governorate, Egypt, during two growing seasons (2022 and 2023). Four Egyptian cotton varieties were used as lines with four genotypes as testers, using line x tester analysis. Results indicated that the genotypes, parents, crosses, parents vs. crosses, lines, testers and line x tester were significant for all studied traits except uniformity index for lines. Most crosses exhibited significantly mid-parent heterosis for most studied traits, while, the crosses Giza95 x Australy13, Giza92 x Australy13, Giza93 x PimaS₆ and Giza97 x Australy13 were significant useful heterosis (better-parent) for most yield traits and fiber properties. The line Giza95 was significant and positive desirable GCA effects for most yield traits except for boll weight, while the lines Giza92 and Giza93 were significant desirable GCA effects for most fiber properties studied. As well as, the tester Australy13 was significant and positive desirable GCA effects for most yield traits studied. The crosses Giza92 x Australy13 and Giza95x TNB1 were significant and positive desirable SCA effects for most yield studied traits. However proportion contribution of lines was higher than of lines x testers interaction and testers for most studied traits. The non-additive genetic variance was larger than additive genetic variance for most studied traits, except for seed cotton yield/plant and lint cotton yield/plant. Heritability narrow sense (h²_b%) estimate was obtained for lint cotton yield/plant which recorded 61.67%, while for lint percentage was recorded moderate values 7.35%. Broad sense heritability estimates (h²_n%) were ranged from 60.85% to 91.25% for uniformity index and micronaire reading, respectively. Generally, Giza95 and Australy13 could be used for improving high yielding cotton varieties in plant breeding programs, while Giza92 and Giza93 considered as beneficial parents for breeding programs to produce new varieties characterized with best the fiber quality