The aim of this study was to determine the effects of thyme (Thymus vulgaris L.), black seed (Nigella sativa L.) essential oils and flavomycin added to the diets on growth performance, carcass characteristics and intestinal organ weights of quails (Coturnix coturnix japonica). One hundred and sixty day-old quails were randomly allocated to four groups, with eight replicate pens per treatment and five birds per pen. The dietary treatments were: 1. Basal diet (control); 2. Basal diet + 10 mg flavomycin/kg diet; 3. Basal diet + 60 mg thyme essential oil/kg diet and 4. Basal diet + 60 mg black seed essential oil/kg diet. Body weight gain, feed consumption and feed efficiency were determined weekly. Carcass and intestinal characteristics were determined at the end of the study (38 day). There were significant effects of dietary treatments on body weight gain and feed efficiency during the first four weeks. The addition of thyme essential oil and flavomycin to the diet resulted in significantly higher body weight gains and better-feed efficiency as compared to that of control group. The supplementation of diet with thyme essential oil decreased abdominal fat weight and abdominal fat percentage. It was found that intestinal weight and length, carcass weight, carcass yield and gizzard weight were not affected by any treatment. At the end of experiment, intestinal pH was lower in groups fed the diets containing thyme and black seed essential oils. It was concluded that the addition of thyme essential oil improved growth performance and tended to decrease the abdominal fat percentage of quails.