Knowledge of type of gene action controlling target traits and genetic behavior is a basic principle for designing an appropriate breeding procedure for the purpose of genetic improvement. Hence, the success of any selection or hybridization breeding program for developing varieties depends on precise estimates of genetic variation components for traits of interest which may be additive, dominant and non-allelic interaction effects. Heterosis and nature of genetic effects on ealiness and yield traits were studied in a 10x10 diallel cross without reciprocals in wheat to define and select efficient and prospective material for immediate use in hybridization programs to improve grain yield of wheat in Iraq. Parents and F₁ were evaluated using (RCBD) with 3 replications for quantitative traits in (2017/2018) season. Significant genotype mean squares and its components (parents and crosses) were obtained for all traits in both generations. Significant heterosis in F₁ generation was obtained for all studied traits. The useful heterosis of grain yield plant^-1 relative to better parent varied from 12.46 to 36.82% in F₁ crosses. The P7(Millan)xP8(Hithab) and P7(Millan)xP9(Ibaa 99) were the best crosses for grain yield heterosis. General (GCA) and specific (SCA) combining ability mean squares were significant for all traits. MS (GCA)/ MS (SCA) ratios indicated the relative importance of additive and additive by additive gene action in their inheritance for all the traits except for earliness and no. of spike plant^-1. The three parents P1(Abu-Graib), P3(Osais), P5(Florka) and P9 (Ibaa 99) gave the highest positive significant  effects for grain yield plant^-1 in the F₁ crosses. Twelve crosses showed significantly desirable heterotic effects for grain yield most studied traits.