Abstract: Five wheat varieties/lines viz., Shahkar-95, Chakwal-86, Fsd-85, Rawal-87 and Pasban-90 were crossed in a diallel fashion to determine the genetic mechanism controlling yield and its components. Spike length, number of spikelet per spike, 1000-grain weight and grain yield per plant were governed by over dominance type of gene action. Number of tillers per plant and number of grains per spike were controlled by additive type of gene action with partial dominance. Epistasis was absent for all the traits studied