The present study was carried out to evaluate whether N-acetylcysteine (NAC) has a beneficial role in enhancing productive and reproductive performance in Inshas layer hens under Egyptian summer conditions. A total number of 300 Inshas hens and 30 Inshas cocks, 34 weeks of age were randomly distributed into 5 groups of 60 hens and 6 cocks each and then subdivided into six replicates (10 hens + 1 cock/ replicate). The first group (G1) was served as the control group without any administration and was injected with water only. The second and the third groups (G2 and G3) drank water supplemented with 50 and 100 mg NAC / litter, respectively, while the fourth and the fifth groups (G4 and G5) were injected with 50 and 100 mg NAC / kg BW, respectively, first three days every month for three months (the experimental period). The obtained results showed that treatment with NAC significantly increased egg production percentage, whereas birds injected with 100 mg NAC/ kg BW recorded the highest value, as compared with those in the control group (68.69 vs. 51.39%, respectively, P