Heterosis and nature of genetic effects on plant growth and yield characters were studied in a 7x7 half-diallel crosses, without reciprocals, in the F1 generation in wheat to define and select efficient and prospective materials to be used in hybridization programs in order to improve grain yield of wheat in Egypt. Parents, F1 were evaluated using a split-plot trail in randomized complete block design (RCBD) with three replications for quantitative characters in 2019/2020 season. Significant genotypes mean squares of parents and crosses were obtained for all characters. Significant heterosis in F1 generation was obtained for all studied characters. The useful heterosis of grain yield/ plant relative to better parent varied from 1.667 to 23.457% in F1 crosses. Two crosses, viz. P1xP2 and P1XP4 had the best values of heterosis for grain yield. General (GCA) and specific (SCA) combining ability mean squares were significant for all characters. Besides, MSe (GCA)/ MSe (SCA) ratios indicated the relative importance of additive gene action in their inheritance for all the characters except number of spikes per plant. The two parents P1 and P5 gave the highest positive significant iĝ effects for grain yield plant-1in F1 generation. The three crosses P1xP2, P3xP6 and P4xP₅ showed significantly desirable heterotic effects for most studied traits. Generally.