The aim of the present study was to estimate different types of gene action affecting some characteristics of tomato fruit. for this purpose , six tomato cultivars were used in this investigation. These cultivars were: (1)  Super Marmand (France) (2) Peto 86 from France (3) Castel Rock (4) Super strain  B, Flora data (5) and Advanced (6) from America.  The varieties were crossed by using complete diallel crosses mating design, in order to produce 30 different hybrids. These parental varieties and their 30 hybrids were evaluated during two seasons for some fruit characteristics. The obtained data were subjected to biometrical analysis and the obtained results revealed that, the mean squares of entries were highly significant for the studied traits, leading to the further partition of genetic variance to its components.. The additive genetic variances were higher than their corresponding values of dominance genetic variances for locules number, fruit firmness, pericarp thickness, total soluble solids, ascorbic acid and lycopene content. The combined data over the two seasons showed that heritability in broad sense (h²b) were 88.8% for locules number of the fruit, 87.3% for fruit firmness, and 78.2% for pericarp thickness,  3.5% for TSS, 95.77% for ascorbic acid,  92.5% for lycopene content. However, heritability estimates in narrow sense (h²n %)were more less than the corresponding values in most of studied traits, indicating that the role of non-additive genetic variance in the genetic expression of these traits are non-negligible. Therefore, the suitable breeding program for improving these traits is recurrent selection programme.