Climate changes are critical global challenges limiting crop development and productivity. Plant breeding is an exceptional solution for providing thermotolerant genotypes. Plant breeding efficiently is a unique solution for providing food security worldwide. The germplasm genetic diversity of cucumber parental lines should support the release of new hybrids. In this study, A half-diallel design mating was performed with six parental cucumber lines to produce 15 hybrids under heat stress conditions in 2019. In 2020 and 2021, all genotypes were evaluated under heat stress conditions, using a randomized complete block design. The analysis of variances revealed significant differences among all genotypes. The mean performance showed that the hybrid, Parent 1×Parent 2 (P1× P2) was the superior hybrid, followed by Parent 1 (P1) for growth and yield components. The descriptive evaluation adequately demonstrated the greatest variation among all genotypes. The genetic distance between parental lines was divided into two groups based on their genetic bases. General combining ability (GCA), specific combining ability (SCA), and heterosis results revealed that P1 and P2 exhibited the highest effects of GCA in the desirable direction for vegetative, yield, and earliness traits. However, P3 showed the highest effect on most fruit traits. According to SCA effects and heterosis, the hybrids P1×P2, P1×P3, and P2×P5 demonstrated superiority in most traits. The selective parents were the good combiners by accumulative selective genes, which could be valuable in hybridization to produce new various prospective hybrids.