Combining ability and heterosis were determined in a population obtained from the full diallel crossing of four different cotton genotypes (G. hirsutum and G. barbadense) for agro morphological traits and yield. High variation was observed for characteristics among parents and the F1 combinations. So, selection could be done for improved yield, yield components and agro morphological traits. Barbadense 5539 and Termeze14 (G. barbadense) had positive GCA for height, bolls/plant and sympodia branch/plant, Inverse, Sahel and Sepid (G. hirsutum) had negative GCA for these characteristics. G. barbadense genotypes showed negative GCA for monopodia branch/plant, sympodia branch length and boll weight, Inverse, G. hirsutm genotypes was observed positive GCA for this traits. The GCA: SCA ratios for the studied traits were higher than one indicating the presence of additive genetic effects for most of the characteristics studied, except for sympodia branch length.