This study was conducted at two locations over two year to determine the extent of genotype by environment interaction and heritability estimates for 35 sunflower genotypes including 10 parents (five cytoplasmic male sterile lines and five restorers/ males and their 25 crosses). The combined analysis of variance across years and locations revealed highly significant differences (P≤0.01) among the genotypes for all traits. The GL and GLY interactions were significant for all traits. The GY interaction was found non-significant for all seven sunflower traits. This indicates that the genotypes were consistent in their performance when tested across years. Variance due to genotypes, (δ2G) was found largest for head diameter (6.60), 1000-seed weight (14.50), seeds head-1 (23722.08), percent oil content (17.71), seed yield (199303.97) and oil yield (46621.56) GY (δ2GY) variance was found largest for days to 50% flowering (3.56) and GLY (δ2GLY). Variance was largest for days to maturity. High estimates of heritability were observed on entry mean basis for 1000-seed weight (0.91±0.24), percent oil content (0.87±1 .24), head diameter, oil yield (0.86±0.22) and seed yield. Low heritable traits were days to maturity (0.10±0.17) and days to flowering (0.35±0.22). Hence flowering and maturity were greatly influenced by the diversity in the two locations and testing of genotypes for these traits over a wide range of locations is suggested to increase heritability.