The aim of the study was to assess whether an extra fertilization with manganese, commercial fertilizer Alkalin (N, K and Si), and combined treatment (manganese + Alkalin) affect the chemical composition of chokeberry fruits (Aronia melanocarpa (Michx) Elliot), especially sugar content and the quantity and profile of phenolics. Dry weight, soluble solids, titratable acidity, total sugar, reducing sugar, sucrose, vitamin C, total polyphenol (gallic acid equivalents); 2, 2-diphenyl-1-picrylhydrazyl radical scavenging activity; and phenolics profile were measured from the fruits harvested from different treatments. Chokeberries treated with manganese showed high content of non-identified phenolic acids [101.15 mg per 100 g fresh weight (FW), these compounds were not detected in fruit treated with Alkalin and manganese + Alkalin], and the highest content of cyanidin glycosides (813.75 mg per 100 g FW). The fruits treated with Alkalin displayed the highest content of quercetin derivatives (40.88 mg per 100 g FW) and eriodictyol 7-glucuronide (26.43 mg per 100g FW). Chokeberries in control treatments had the highest content of dry weight (30.76% FW), soluble solids (24.1% FW), total sugar (20.92% FW), vitamin C (8.4 mg 100 g–1 FW), total polyphenol (2377.1 mg gallic acid equivalents per 100 g FW), the highest 2, 2-diphenyl-1-picrylhydrazyl radical % inhibition (38.1%), highest content of chlorogenic acids (210.38 mg per 100 g FW), (-)epicatechin (32.18 mg per 100 g FW) and the highest degree of procyanidin polimerization (59). The results indicate that applied fertilization exerted differential influence on chemical composition of aronia fruits.;