The search for agrotechnical alternatives that improve crop yields while having a neutral impact on the environment is the essence of sustainable agriculture. Biostimulants are an important tool for integrated crop management. The objective was to assess the biostimulating activity of macerates from the leaves of Levisticum officinale L., using soybean as a model crop. The extract was evaluated for biologically active compounds as well as its ability to support the growth of soybean plants in natural conditions during a three-year field experiment. The effect of macerates on morphophysiological parameters of soybean plants was evaluated. The harvested crop was analyzed for its mineral profile, protein and amino acid content, including essential amino acids, fat and fatty acids, and fiber fraction content. The analysis showed that the lovage root extract contained antioxidants in the form of phenolic compounds, soluble carbohydrates, minerals, and phytohormones. The concentration of bioactive compounds indicates that the plant extract has agronomic potential and can be considered an effective natural biostimulant to improve soybean growth and yield. The bioactive components of the lovage extract played an important role in plant growth and metabolism. The number of pods per plant and soybean yield increased significantly after the application of the macerate. The concentration of minerals, amino acids, and total protein in soybean increased by the application of lovage macerate. The analyzed extract is an effective natural biostimulant and can be used in agricultural practice.