Abstract <p>The article examines the effect of traditional mineral fertilizers (ammonium nitrate, superphosphate, and potassium chloride), slow-release complex fertilizers (Osmocote, Ruscote), and foliar treatment with lignohumate on the content of macronutrients (nitrogen, phosphorus, potassium), phenolic compounds, and anthocyanins in the leaves and berries of black currant (<i>Ribes nigrum</i> L.) over a 3-year experiment. The research was conducted on one-year-old seedlings in the soil station at Moscow State University. The highest phenolic compound content was observed in leaves with the application of traditional fertilizers (1.9 mg GAE g^–1 DW) and Osmocote (1.8 mg GAE g^–1 DW) in 2022. The highest phenolic concentration in berries (1.1 mg GAE g^–1 DW) was recorded in 2023 with traditional fertilizers. Positive correlations were identified between macronutrient content in soil and plants and the phenolic compound levels in plant samples, highlighting the importance of nitrogen and phosphorus in their biosynthesis. It was found that fertilization reduced anthocyanin concentrations in berries (from 196.7–219.5 to 105.3–111.7 mg kg^–1 fresh weight), which may be attributed to reduced plant stress. The highest nitrogen accumulation in leaves and berries was observed with traditional fertilizers (1.9 and 1.1%, respectively), while the highest phosphorus and potassium levels were recorded with Ruscote (phosphorus: 0.8 and 0.6%, respectively; potassium: 1.2 and 0.7%, respectively). The findings emphasize the importance of optimizing fertilization practices to enhance the nutritional value and antioxidant potential of black currants.</p>