Melon is an economically important crop and Iran is considered as its diversity center. To investigate gene action, heritability and number of effective factors for yield and related traits, six generations, namely: P1, P2, F1, F2, BC1, and BC2 of two crosses of Mirpanji × Tashkandi and Mirpanji × Abasali were produced and evaluated in the spring of 2008, applyig a complete block design of three replications. Significant differences were observed among generations for all the traits. In Mirpanji × Tashkandi, a positive significant cross heterosis over the more dominant parent was found for yield as well as for the acceptable yield (13.76 and 27.34% respectively). Estimates of gene effects as based upon a six-parameter model (according to Mather and Jinks in Mirpanji × Tashkandi cross) showed that a simple additive-dominance model is adequate for the evaluated characteristic except for days to maturity and for fruit length. Both additive and dominance gene effects were important in the governing and acceptable yields in Mirpanji × Tashkandi cross, while epistatic genetic effects were not important. Chi square and Joint Scaling Tests in Mirpanji × Abasali cross indicated that a simple additive-dominance model was not adequate for the evaluated characteristic, while epistatic genetic effects did prove their importance.