To evaluate gene effects and heritability of fruit and flower characters in melon, three experiments were performed. In the first experiment, 48 genotypes of different melon groups were planted to choose the monoecious melon. To investigate the sex modification regarding fruit traits, seven parents, including a monoecious type and andromonoecious types, crossed in a full diallel scheme to obtain all possible combinations. Evaluation amongst all genotypes revealed one Cantaloupensis and all Flexuosus genotypes with monoecious flowers. Floral and fruit characters of F1 hybrids obtained from the diallel cross, were recorded. All hybrids that have been crossed with the monoecious parent revealed the monosexual progenies. Most of the floral characters with high GCA/SCA values remarked the additive gene effect. There were also cytoplasmic effects on flower and fruit traits. The significant GCA /SCA estimates observed for fruit traits such as yield, fruit length, fruit length to width, flesh thickness referred to the importance of additive gene effects. It could be demonstrated that classic hybridization holds great potential in controlling flowering habit and yield‐related fruit traits.