This study was conducted to investigate the effect of dietary sericite(SC) on laying performance, feed conversion ratio, egg quality and fecal ammonium nitrogen. Three hundreds and sixty 92-wk-old, Lohman Lite layers were randomly divided into 20 groups of 18 birds each and assigned to five experiment for 4 weeks (72 birds per treatment). Dietary treatments were Control (control diet), SC 0.5 (control diet +0.5% sericite), SC 1.0 (control diet +1.0% sericite), SC 1.5 (control diet +1.5% sericite), and SC 2.0 (control diet +2.0% sericite). Hen-day egg production tended to increase by the SC 1.0%, SC 1.5% and SC 2.0% supplementation in the diets. Egg weight also tended to increase by the SC 1.0% addition in the diets. Feed intake was increased (p<0.05) in SC 1.5 and SC 2.0 but feed conversion was improved (p<0.05) only in SC 1.0 (p<0.05). Digestibility of nutrients were not linearly affected by dietary supplementation of sericite although there was an inconsistent difference. Egg shell strength, albumin height, yolk color, and egg shell thickness were not affected (p<0.05) by treatments. Fecal NH3-N concentration was decreased (p<0.05) by dietary sericite supplementation compared to control. This study showed that dietary 1.0% sericite supplementation can be beneficial to improve egg production, egg weight and feed conversion and to decrease fecal NH3-N concentration.