This study was conducted to evaluate the effects of dietary supplementation of humic acid (HA) on reproductive performance, egg production, some blood parameters and carcass traits of turkey hens. A total of 160 turkey hens from White Holland strain were employed in a completely randomized block design with one control group and three treatment groups. Each group was divided into four replicates (10 hens in each). Diets of the 1^st, 2^nd, 3^rd and 4^th groups were supplemented with 0, 200, 300 and 400 mg HA/kg diet, respectively. Results showed that all HA levels increased (P<0.05) live body weight, feed conversion, egg production and egg quality in terms of increasing (P<0.05) egg yolk index, Haugh units and shell thickness, while albumen, yolk and shell percentages, shape index and yolk color score of eggs were not affected by HA. Fertility and hatchability rates were improved (P<0.05) by all HA levels. Count of red and white blood cells in whole blood and albumin concentration in blood plasma increased (P<0.05) by all HA levels as compared to control, being the highest for HA at a level of 300 mg/kg at all age intervals. Activity of AST and ALT and concentration of thyroid hormone (T₃) in blood plasma were not affected by HA. Carcass traits showed in terms of weight of carcass, liver, gizzard, spleen and oviducts relative to live body weight were the highest (P<0.05) in hens fed HA diets at levels of 300 and 400 mg/kg diet. Based on the obtained results, it could be concluded that dietary humic acid supplementation in turkey diet markedly improved reproductive performance, egg quality and carcass traits without adverse effects on healthy status of laying hens.