We aim to study biologically active agents in biological substances obtained from different parts of red deer antlers. Frozen red deer antlers were separated into skin and antler base, crushed, and subjected to ultrasonic enzymatic hydrolysis. The press cake from the extraction of antler base was dried in a vacuum unit. The content of protein, fat, ash, and moisture in the obtained biological substances was studied. In addition, the amino acid, fatty acid, and mineral compositions were analyzed, as well as the molecular weight distribution of peptide fractions. The concentrates from the skin and base of red deer antlers were found to contain the maximum of proteins (73.68–74.41%). The mineral biological substances comprise the maximum of macroand microelements (84.17%), in particular, a high level of 136,000 mg /kg of phosphorus, 29,230 mg /kg of sodium, and 5,140 mg /kg of calcium. All biological substances are characterized by a low-fat content in the range from 0.3 to 1.76%. Similar to the protein content, the total amount of amino acids prevails in concentrates from the skin and base of red deer antlers, equaling 40.90 and 43.66 g /100 g, respectively. Moreover, in both samples, the amount of essential amino acids is higher than that of non-essential ones. The amount of vitamins is low, being represented by B1, B2, B6 water-soluble vitamins. The fatty acid composition is most balanced in the concentrate from the red deer antler base, containing omega-3 and omega-6. The ratio of unsaturated to saturated fatty acids is equal to 0.96. In the concentrate from antler skin, the maximum content (54.7%) of peptides with a low molecular weight of less than 2.9 kDa and up to 6.4 kDa was found using the molecular-weight distribution of peptide fractions.