A total of 240 day old chicks were used in a completely randomized design to investigate the effects of Thyme essence, in aflatoxin B1 contaminated diets on the internal organ weights, biochemical traits and mortality of broilers. Twelve pen replicates with 20 chicks in each pen were assigned into each of the 4 dietary treatments having 3 replicates comprising: 1) basal diet containing; 2) basal diet + 600ppb aflatoxin; 3) basal diet + 500ppb Thyme essence; and 4) basal diet + 600ppb aflatoxin + 500ppm Thyme essence. The addition of aflatoxin to diets reduced spleen weight and increased the liver weight and inclusion of Thyme essence could only restore the increased liver weight. Aflatoxin increased the cholesterol, LDL and HDL levels in the broilers blood and Thyme essence cold partially reduce these increased levels. In conclusion, results of the present study indicated that the Thyme essence is a partially useful effective for reducing the signs of aflatoxin B1 toxicities in growing broilers.