Thyme essential oil (TEO) was evaluated for its ability to reduce the deleterious effects of AF in Japanese quail. It was incorporated into the diets containing 2.5 mg/kg total AF. In the present study, 120 10-d-old Japanese quail were randomly distributed into four experimental groups (30 birds per group) and fed the following diets for 35 days: I) Control (C): bazal diet; II) C+2.5 mg/kg AF; III) C+0.1% TEO; IV) C+2.5 mg/kg AF+1% TEO of diet. Each treatment consisted of 10 repli-cates of 3 quail. Performance parameters were determined weekly. Feed were given as ad libitum. Results showed that by the end of the trial, feeding alone AF-containing significantly decreased body weight gain and feed consumption during the exper-iment. The addition of TEO to an AF-containing diet significantly reduced the deleterious effects of AF on body weight gain and feed consumption. Body weight gain was reduced by 16.3% in quail consuming the AF diet without TEO, but increased by 1.7% for quail consuming the AF plus TEO diet. Similarly, feed consumption was reduced 17.3% in birds consuming the AF diet without TEO, but by only 2% for birds consuming the AF plus TEO diet. Feeding TEO alone caused significant im-proved in feed conversion ratio during the experiment compared with the other groups. These results suggest-ed that TEO effectively diminished the detrimental effects of AF on performance in this study.