The study aimed to determine the yield structure parameters of four winter wheat cultivars depending on the application of biologically active compounds and fertilizer rates under the conditions of the Ukrainian Forest-Steppe. The research was conducted during 2023–2025 at the Bila Tserkva Research and Breeding Station of the Institute of Bioenergy Crops and Sugar Beet (NAAS), located in the South-Western Forest-Steppe of Ukraine. A three-factor field experiment was established using a randomized plot design in four replicates. The study evaluated different treatment schemes: 1 – seed treatment (Rizofos Liq 1.5 L/t + Premax 0.3 L/t, Mycofriend 1.5 L/t), 2 – soil application of a biological product during sowing (Groundfix 3.0 L/ha) (Factor A). Mineral nutrition was provided by applying N12P12K12 and N24P24K24 fertilizers during sowing (Factor B). For control was used variant without use of biological products and without fertilization. Four winter wheat cultivars were selected for the study: ‘KWS Spencer’, ‘Maurizio’, ‘Matchball’, and ‘Vidrada’ (Factor C). It was established that the use of biological products in winter wheat cultivation positively affects the formation of productive stems, grain number per spike, grain mass per spike, and biological yield. All factors and their interactions were statistically significant. Factor B (mineral fertilization) had the most substantial impact on yield structure, with a contribution of 46.68-78.03% depending on the parameter. The influence of Factor C (cultivar) ranged from 10.35% to 28.20%, while Factor A (biological product) accounted for 1.52-12.51%. The combined application of Rizofos Liq (1.5 L/t) + Premax (0.3 L/t) with the N12P12K12 fertilization rate ensured the maximum increase in all yield structure components, resulting in a biological yield of 5.7-7.4 t/ha. Under similar conditions, the grain yields were 6.8 t/ha for ‘Maurizio’, 6.1 t/ha for ‘Matchball’, and 5.7 t/ha for ‘Vidrada’. The obtained biological yield figures correlate with the number of productive stems per linear meter and the 1000-grain weight.