The effect of humic substances on growth performance, excretion, and the digestive organs was studied in pheasant chickens. Three hundred 1-day-old pheasant chicks were assigned to two equal groups. Chicks in the experimental group were fed diets supplemented with humic substances (5 g/kg). Chickens in the experimental group reached significantly higher average daily weight gains (p ˂ 0.05) in the second phase of rearing (29–49 d) at a significantly better feed conversion ratio (p ˂ 0.05). The supplementation of humic substances led to a significant increase in the average body weight of pheasants at the end of the experiment (p ˂ 0.05), and to a significant increase in average daily weight gains for the entire monitored period (p ˂ 0.05). In the experimental group, significantly higher relative weights of the gizzard (p ˂ 0.05), small intestine (p ˂ 0.05), and jejunum (p ˂ 0.05), along with a significantly larger relative length of the duodenum (p ˂ 0.05), were recorded. A significantly higher concentration of dry matter in the droppings of pheasants was found in the experimental group than in the control group (p ˂ 0.05). According to our results, feeding humic substances had the most beneficial effect on pheasant growth performance during the growing phase. Humic substances can also have a positive effect on the microclimate within the breeding facility. Reductions in the water content of droppings contribute to a reduction in the humidity of the litter, thus limiting the activity of nitrogenic bacteria.