Aronia melanocarpa (Michx.) Elliott, ×Sorbaronia fallax (C. K. Schneid.) C. K. Schneid. nothosubsp. fallax, and ×Sorbaronia fallax nothosubsp. mitschurinii (A. Skvortsov & Maitul.) A.Stalažs, belonging to the Rosaceae family, are grown as fruit plants. They are known to horticulturists as garden chokeberry or black chokeberry. The fruit of these species is the richest source of biophenols in the plant kingdom and suitable raw material for the production of functional foods with high nutraceutical value. The work aimed to examine the basic and polyphenolic composition of fruit chokeberry and rowan-chokeberry hybrids of different taxonomic groups. Experimental plants were grown at the orchard of the National University of Life and Environmental Sciences of Ukraine in the Kyiv region. Fruit of 10 cultivars developed in Belorussia, the Czech Republic, Finland, Russia, Ukraine, and the USA were collected during 2020 and 2021. The fruit was analyzed for dry matter, soluble solids, sugars, pectin substances, organic titratable acidity, ascorbic acid, and biophenols. Chokeberry fruit contains on average 24.4–29.2% dry matter, 16.0–21.1% soluble solids, 6.5–8.9% sugars, 0.40–0.80% pectin, and 0.95–2.15% organic acids on raw material. Bioactive components of chokeberry fruit are ascorbic acid (24.7–45.9 mg/100 g), total polyphenols (998–4840 mg/100 g), including anthocyanidins (9–217 mg/100 g), flavonoids (23–1422 mg/100 g), and chalcones (9–59 mg/100 g). If the group ×S. fallax nothosubsp. mitschurinii cultivars is morphologically constant and like A. melanocarpa simple in leaf shape, then the group ×S. fallax nothosubsp. fallax cultivars was different in the morphology of leaves from lobate to pinnate and fruit color from purple to black in the study. Chokeberry fruit composition varied between each year and especially between taxonomic groups and cultivars. Fruit harvested in 2021 had the lowest dry matter, soluble solid, sugars, and ascorbic acid in comparison with 2020. In contrast, titrated acidity was consistent between years. The fruit of garden chokeberries is a good source of ascorbic acid. ×S. fallax cultivars with the exception ‘Titan’ are richer on ascorbic acid. The fruit of A. melanocarpa ‘Dwarf’ has the highest content of total polyphenols, flavonoids, and chalcones. There are significant differences between ×S. mitschurinii cultivars in biochemical content. Purple-fruited ‘Titan’ has the lowest content of all biologically active substances, than other cultivars belonging to the same ×S. fallax taxonomic group. The black-fruited ×S. fallax nothosubsp. fallax genotypes, including the first chokeberry cultivar ‘Vseslava’ of Ukrainian breeding, often have a high or the highest content of ascorbic acid, total polyphenols, anthocyanidins, flavonoids, and chalcones, which is valuable for garden chokeberry breeding.