In the present research, divergent selection for Japanese quail body weight at four and five weeks of age was performed in five generations to estimate the response to selection and realized heritability. The average body weight was significantly (p<0.01) different among lines selected for increasing (HW) vs. decreasing (LW) weight. Cumulative responses to selection for four and five weeks of age body weight during five generations for males and females were respectively 21.15, 18.98 and 18.662, 15.65 in HW line while -22.14, -28.152 and -22.33, -29.47 grams for LW line. The value of realized heritability of body weight for females was higher than that for males in all the lines, with its value decreasing with increase in the age of birds. Selected lines for decreasing body weight showed a higher heritability than the lines selected for increasing body weight. Differences between male and female were significant in all the generations except in generation four. Body weight average varied between the selected and control lines for all the generations.