In any breeding program, knowledge of the nature of gene action involved in the inheritance of traits is a basic requirement. In this research, diallel crosses progenies of six coriander landrace were evaluated in F₁ and F₂ generations. The genotypes were evaluated in different irrigation conditions in three separate experiments, in which each experiment was conducted in a randomized complete block design with three replications during the growing season of 2016. Results of genetic variance analyses revealed significant mean squares of general and specific combining ability for all traits, indicating the importance of additive and non-additive genetic effects for these traits. Additive gene actions played a more important role in controlling of plant height, leaf number, branch number and biological yield, whereas the role of non-additive gene actions was more conspicuous than those of additive gene actions in controlling of harvest index and fruit yield. Therefore, providing superior hybrids using breeding methods based on progeny test will be effective to improve these traits. Also, among selected parents, P₄ parent in normal irrigation and moderate water stress and P₆ parent in sever water stress were the best parents for crosses in the development of high-yield varieties in coriander.