Abstract. The aim of the study is to evaluate the effect of phytobiotics on the biochemical composition of the muscle tissue of broiler chickens. Research methods: atomic emission spectrometry, capillary electrophoresis, gas chromatography. Scientific novelty. The influence of phytomaterials (gamma-octalactone, vanillic acid) on the biochemical composition of the muscle tissue of broiler chickens was evaluated for the first time. Results: biochemical composition of muscle tissue the composition was characterized by a lower content of amino acids: tyrosine (pectoral muscles), lysine, threonine, alanine, leucine + soleucine (femoral muscles) in group II (P < 0.05) and a high content of valine and histidine (pectoral muscles) in group I (P < 0.05), according to compared to the control. There was also an increase in the concentration of fatty acids in the pectoral muscle (P < 0.05): myristic and arachin (I and II), stearic (III), linoleic (II and III) and a decrease in palmitic (III) and palmitooleic (II and III). An increase in the concentration of myristic (III group, P < 0.05), oleic (II group, P < 0.05) fatty acids was found in the thigh muscles. In group I broiler chickens, the concentration of macronutrients (Ca, P, K, Na) and trace elements (B, Fe) in the pectoral muscle decreased (P ≤ 0.05). In group II, an increase was found (P ≤ 0.05) – Ca, Co, Mn, Zn, in group III – Fe (P ≤ 0.05). In the thigh muscle tissue of group I, the concentrations of macronutrients – K, Mg decreased (P ≤ 0.05) and increased (P ≤ 0.05) Na, Ca, B, Cu, Ni, I, Zn. In II, there was an increase in the content of B (P < 0.05), and in III, on the contrary, a decrease (P ≤ 0.05) in Ca and K. Thus, the use of vanillin acid alone or in combination with gamma-lactone contributes to the biological value of the muscle tissue of broiler chickens in terms of increasing the amount of essential amino acids, unsaturated fatty acids and important macro- and microelements.