Heterosis and nature of genetic effects on plant growth and some yield characters were studied in a 6x6 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 randomized complete block design (RCBD) with three replications for quantitative characters in 2019/2020 season. Significant genotype 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 total yield/ plant relative to better parent varied from 16.50 to 33.95% in F1 crosses. Two crosses, viz. P3xP5 and P5XP6 had the best values of heterosis for total yield. General (GCA) and specific (SCA) combining ability mean squares were significant for all characters except No. of tellers/plant. Besides, MSe (GCA)/ MSe (SCA) ratios indicated the relative importance of additive gene action in their inheritance for maturity date and height up to flag leaf in to locations, No. of tillers / plant in to location one, total plant weight, straw. The two parents P2 and P3 gave the highest positive significant iĝ effects for total yield plant-1in f1 generation. The three crosses P1xP3, P3xP5 and P5xP6 showed significantly desirable heterotic effects for most studied traits.