The laying performance and egg quality parameters were studied after Gamma-aminobutyric acid (GABA) supplementation in laying hens. One hundred and fifty Lohmann Brown laying hens (32 weeks old) were randomly allotted to 3 treatments: control (without drug), GABA (40 mg/kg b.wt) and GABA (80 mg/kg b.wt). Each group consisted of 5 replicates of 10 hens and given the medication orally, daily for 4 weeks. The laying performance parameters (egg production, egg weight, egg mass, and feed conversion ratio) were improved after oral administration of GABA (80 mg/kg b.wt) compared with control. Higher egg shape index, shell weight, and shell thickness were recorded in the GABA (80 mg/kg b.wt) supplemented group compared with control. The egg yolk quality parameters (yolk weight, yolk index, and yolk color) and albumin quality parameters (albumin weight, albumin index and albumin haugh unit) were improved by using 80 mg GABA/kg b.wt. The egg yolk cholesterol and triglycerides concentrations were decreased in both GABA treated groups when compared with control. In conclusion, the best laying performance and egg quality parameters were obtained by oral medication of a higher dose of GABA in drinking water of layers. The two doses of GABA induced low-cholesterol and triglycerides concentrations in egg yolk and this experiment showed that GABA is a valuable supplementation for layers in drinking water.