Five wheat lines namely, SARC-1, 243/1, 6142, 8244 and 5039 were crossed in a diallel pattern to determine the mode of gene action for some morphological traits like flag leaf area, number of tillers per plant, peduncle length, number of spikelets per spike and 1000-grain weight. The analysis of variance revealed that there were highly significant differences among the lines for all the traits under discussion. Over-dominance type of gene action was found for flag leaf area, number of tillers per plant and 1000-grain weight. While peduncle length and number of spikelets per spike were controlled by partial dominance with additive type of gene action. Non-allelic interaction was absent for all the characters. The genotypes 243/1 had maximum dominant genes for number of tillers per plant and peduncle length. Maximum dominant gene were noticed in 6142 for flag leaf area, while 5039 possessed maximum dominant genes for number of spikelets per spike. Similarly, genotype 8244 contained maximum dominant genes for the important character 1000-grain weight. Selection for flag leaf area, number of tillers per plant and 1000-grain weight would be ineffective in early generation, while it would be effective for peduncle length and number of spikelets per spike.