A study was conducted at Barakat Abul- Fadhul Station located in Kerbala province for Sheep Production on a total of 63 pregnant ewes from two local breeds (36 Nuimi and 27 Awassi) to find out the association of growth hormone gene polymorphism with the body weight performance of lambs at two stages of life, birth and weaning stages. Polymerase Chain Reaction–Restriction Fragment Length Polymorphism (PCR-RFLP) technique was used to detect polymorphism of growth hormone gene by using restriction enzyme (Hae III) to determine fragment of 422 base pair from growth hormone gene. Lamb weights at birth and at weaning age were measured. The results revealed that 3 genotypes of growth hormone gene were detected in both breeds (AA, Aa and aa) with significant effect of genotypes on mean birth and weaning weights in both breeds. The results also indicated that AA genotype in Nuimi breed recorded the highest value (6.35±0.70 kg) in the mean birth weight and (21.50±3.50 kg) in mean weaning weight with a significant effect (P˂0.05). However, the results of Awassi breed reported that aa genotype had highest values in the mean birth weight (6.82±0.68 kg) with a significant effect (p˂0.05) and mean weaning weight was (23.09±1.50 kg).