The basic chemical composition, bioactive compounds, and antioxidant capacity of fruits of three new Polish breeding clones (No. 5/6, type S, and type N) and four Canadian cultivars (cvs.) (“Martin”, “Smoky”, “Pembina”, and “Honeywood”) grown in Poland in 2016 were investigated. Fruits were analyzed for their contents of triterpenoids, carotenoids, chlorophylls, and polyphenolics with the ultra-performance liquid chromatography photodiode detector-quadrupole/time-of-flight mass spectrometry (UPLC-PDA-Q/TOF-MS) method, sugar with the high-performance liquid chromatography–evaporative light scattering detector (HPLC-ELSD) method, and antioxidant capacity with the ability to reduce free radical (ABTS) and ferric reducing ability of plasma (FRAP) method. Thirty-eight bioactive compounds, including twenty-eight polyphenolic compounds (four anthocyanins, nine phenolic acids, nine flavonols, and seven flavan-3-ols), four carotenoids, two chlorophylls, and three triterpenoids were identified in the fruits. The fruits of the tested Saskatoon berry genotypes were found to be rich in phenolic compounds (3773.94–6390.36 mg/100 g·dm), triterpenoids (66.55–91.31 mg/kg·dm), and carotenoids (478.62–561.57 mg/kg·dm), with high ABTS and FRAP capacity (10.38–34.49 and 9.66–25.34 mmol·Trolox/100 g·dm, respectively). Additionally, the berries of these genotypes seemed to be a good source of sugar (9.02–19.69 g/100 g), pectins (0.67%–1.33%), and ash (0.59%–0.67%). Some genotypes of Saskatoon berry, especially the clones type S, type N, and cvs. “Honeywood” and “Smoky”, may be selected for their potential applications in commercial cultivation to produce fruits with valuable health-promoting nutritional effects on human health. Additionally, three new genotypes that may offer new functional materials can be recommended for fruit growers.