The study aims to optimize the formation of soybean quality indicators according to varietal characteristics and weather conditions of the northeastern forest-steppe of Ukraine. During the experiment, among the studied varieties, the highest weight indicators of 1,000 seeds (190.4–202.4 g) were formed by varieties such as Asuka, Diadema Podillya, Tenor, and Millennium, significantly higher than the weighted average value for the group of studied varieties (Duncan test = 15.3 g). The largest seed was formed under the conditions of 2020 (180.7 g). During the 2019–2021 study period, varieties such as Titan, Paradis, Tenor, and Kyoto (40.5–41.0%) had the highest protein content on average. In terms of the years studied, 2020 was marked as the most favorable; under its weather conditions, the varieties formed an average of 40.1% of the protein in the grain. The Vinni, Navigator, Alaska, Knyazhna, Amadea, Oriana, Triada, Merlin, and Arisa varieties showed significantly higher fat content than the average (19.8–20.7%). Seeds harvested in 2019 had the maximum oil content on average (20.0%). The study of the amino acid profile of different soybean varieties revealed significant variations in essential and non-essential amino acids. The Tytan variety is characterized by the highest levels of lysine (2.99 g/100 g), leucine (3.42 g/100 g) and alanine (1.83 g/100 g). In contrast, the Tenor and Cordoba varieties show the lowest levels of these amino acids (1.70–1.71 g/100 g lysine, 2.26–2.43 g/100 g leucine, and 1.33–1.40 g/100 g alanine, respectively). High levels of threonine are also observed in the Vinni and Tytan varieties (1.80–1.88 g/100 g). The maximum concentration of methionine was noted in the varieties of Favor and Tenor (0.08–0.09 g/100 g), while in most other varieties, the content of this amino acid did not exceed 0.03–0.04 g/100 g. Tenor, Arisa, Tytan, Vezha, and Vinni are the leaders in the content of valine, isoleucine, phenylalanine, proline, glutamic, and aspartic acids, respectively. In contrast, the varieties of Alaska, Diadema Podillya, and Cordoba are characterized by the lowest content of these amino acids. The highest histidine content (1.90 g/100 g) was recorded in the variety of Samorodok, and the lowest (1.21–1.27 g/100 g) was recorded in the varieties of Tenor and Cordoba.