This study was carried out to determine the effects of peppermint (Mentha Piperita) on blood parameters (cholesterol, triglyceride (TG), high density lipoprotein (HDL), low density lipoprotein (LDL), malondialdehyte (MDA), antioxidant activity (AOA), total protein, glucose, carcass yield, heart, liver weights and organoleptic control of the carcasses in laying quails. A total of 180 15 week old laying quails were used in the study. There were 5 experimental groups which were supplemented with different ratios of Peppermint up to 5%. The control group received no peppermint supplements. The experiment continued for 10 weeks. Antioxidant activity and HDL amounts increased (P<0.05) in parallel with the increase of peppermint supplementation, while LDL, glucose, MDA amounts decreased (P<0.05) with the increase of supplemented peppermint. No effects were observed (P>0.05) on the carcass quality with a 5 % peppermint supplementation to the diet. In conclusion, the supplementation of peppermint to diets up to a 5% level was found to be quite beneficial in terms of blood parameters such as MDA, AOA, LDL, and HDL.