This study was to evaluate selective breeding on body weight over three generations in Japanese quail and to understand the association between three GH gene SNPs and growth. The analysis included the average body weight at 2, 4, and 6 weeks of age which showed an increasing direction from the basic population to generation three (G3). The most significant growth observed was at 2-weeks where there was a 35.8% increase by G3 signifying good early growth selection. The results also evaluated selection response, selection differential as well as realized heritability for 4-week bodyweight thus demonstrating strong genetic response during first generation (G1 by 35.8% increase) but reduced responses in subsequent generations. Genotypic analysis was done using SNPs located within growth hormone gene showing frequency shifts among different alleles. Different SNP genotypes consistently correlated higher than usual weights thus giving pointers towards future breeding strategies; additionally additive effects varied across generations which implies need for specific approaches aimed at manipulating genes responsible for controlling weight gain within particular periods during ontogeny while taking care not to interfere with other important biological processes occurring simultaneously. The study therefore showed that (BV) breeding values for 4-week body weight increased significantly between G1 and G3 but subsequent increases became smaller indicating possible genetic limits being reached. In conclusion, this study was significant for Japanese quail industry because it will help farmers optimize their breeding plans towards attaining desired weights using selective breeding methods during early maturity periods too.