This experiment was conducted to investigate the effects of thyme of medicinal plant on performance, carcass characteristics and blood biochemicalwere studiedinJapanese quails.In this experimentat first 300one week old japanese quails were divided to 5 groups and 3 replicates of 20 chicks in each group. Experimental groups included G1, control group with no thymesupplementation, G2, G3, G4, and G5 received 0.75% ,1%, 1.5%, and 2% Thymerespectively. The results showed that the use of different levels of Thymehas significant effects on performance and carcass traits (P<0.05). The highest level of average daily gain, spleen and liver were in group 5 but the greatest percent of gizzard was observed in group 4.Also the serum total cholesterol and triglycerides concentration were significantly reduced in groups of 4 and 5 compared to the control group (P<0.05). The results evidence that the using of thyme in Japanis guils have significantly effects on performance and blood biochemical and carcass traits.