The substitution effect of maize grain with grain milling by-products (GMP) was investigated on egg production and fertility parameters in White Leghorn layer hens. To this effect, four treatment (T) diets were formulated to contain GMP (g/kg) at zero (T1), 100 (T2), 150 (T3) and 200 (T4) by partially replacing the maize grain. Onehundred forty four White Leghorn layer hens were allocated randomly to the treatment diets, replicated thrice consisting of 12 hens each. The experiment was conducted for 20 weeks. The results indicated that the hen-housed egg production and daily egg mass output was higher (p<0.001) in hens fed with T1 and T2 diets than those of T3 and T4. Birds fed with T1 diet produced heavier (p<0.001) eggs than those reared in T2, T3 and T4 diets, the former being significantly different with the latter two. The daily feed intake differed significantly among treatment diets being higher (p<0.001) in birds fed with T1 and T2 than that of T3 and T4 diets, which had similar values. No significant difference was observed in hen-housed egg production, daily egg mass output, and daily feed intake among hens fed with T1 and T2 diets. Similarly, no significance difference was observed in egg weight, total and daily feed intake between hens fed with T3 and T4 diets. The feed conversion ratio (FCR, kg feed/kg egg mass) were different among treatment diets in which the lowest value being observed in those chickens reared in T1 followed by T2 diets. Birds fed with T4 diet had the highest FCR as compared with the rest of the treatment groups. Fertility and hatchability of eggs set were similar among chickens reared in T1 and T2 diets; but were higher (p<0.05) than those of T3 and T4 which had similar values. However, hens fed with T4 diet had lower (p<0.05) value in hatchability of fertile eggs than the rest of other treatments. In conclusion, the substitution of maize grain with 10% GMP showed similar effect with that of the control group in all studied performance parameters. Thus, GMP could be safely incorporated in replacement of maize for layer hen diets up to 10%.