The aim of the present study was to investigate the usage of thyme leaves and its effects on performance, some egg quality traits and humoral immunity in laying hens. A total of 108 laying hens aged 36 weeks were randomly assigned to three dietary groups for 16 weeks. Dried and ground (Thymus vulgaris L.) thyme leaves were used at the level of 0, 1 and 2% in the diets of groups. Feed intake, body weight, egg production, egg weight and egg quality characteristics were not affected by dietary thyme supplementation. Thyme supplementation at 2% resulted in beneficial effects in laying hens due to the lowering of yolk cholesterol and total saturated fatty acids concentration while increasing omega-3 fatty acids. Furthermore, the yolk malondialdehyde, blood serum cholesterol and triglycerides levels were reduced and antibody titers against SRBC were increased with 2% thyme supplementation. In conclusion, the results showed the antioxidative and hypolipidemic effects of thyme supplementation in laying hens along with improved humoral immune response without any negative effects on performance and egg quality characteristics.