Twenty four diploid cotton hybrids along with parents and checks were evaluated during kharif 2011-12 at Main Agricultural Research Station, Dharwad to estimate the level of heterosis. The analysis of variance revealed that the parents and hybrids differed significantly for all the characters under study indicating presence of considerable genetic variability between the genotypes. Two thermo sensitive genetic male sterility based hybrids (Pl-38 x A-2 and Pl-38 x QT-14) exhibited higher level of heterosis over mid parent, better parent and standard checks for seed cotton yield and its component traits . Pl-12 x A-1 exhibited higher level of heterosis over mid parent, better parent and DLSa-17 for seed cotton yield and its component traits. The highest yielding cross Pl-38 x A-2 expressed highest significant mid parent heterosis (347.44%), heterobeltiosis (249.82%), standard heterosis over check DLSa-17 (106.23%) and hybrid check G.Cot.MDH-11(30.19%) for seed cotton yield per ha.