The ban on the use of antibiotics as growth promoters has stimulated the search for alternative feed supplements in poultry production. The active principles of thyme essential oil act as a digestibility enhancer, balancing the gut microbial ecosystem and stimulating the secretion of endogenous digestive enzymes and thus improving growth performance in poultry (Lovkova et al., 2001; Williams and Losa, 2001). A study was performed to investigate the effects of thyme essential oil (TEO) on performance, carcass characteristics, some blood parameters and ileal microflora of Japanese quail. This study lasted 35 days of age. One hundred and fifty day-old male Japanese quail chicks in a completely randomized design with two treatments (with or without 1 g/kg TEO) and five replicates of 15 birds each were used. All parameters were measured at the end of the experiment. The supplementation of TEO significantly (P<0.05) increased live body weight and relative weights of carcass and breast, lowered serum triglyceride, total cholesterol and glucose and improved ileal microflora. It was concluded that the addition of 1 g/kg TEO might offer some beneficial effects on Japanese quail to increase live body weight and improve some blood parameters and gut miroflora.