The objective of the research paper was to assess the potential usefulness of American cranberry fruits and leaves to produce health-promoting food products. The research comprised leaves and ripe fruits of 4 American cranberry varieties: ‘Bain Favorite’, ‘Ben Lear’, ‘Drewer’, and ‘Earli Richard’. In fresh berries determined were the major parameters of chemical composition: dry substance, extract, total sugar content, acidity, vitamin C content, and pectin content. Methanol extracts were prepared from the lyophilized fruits and leaves; therein, the content of polyphenolic compounds was determined by a liquid chromatography method (UPLC), as were the antioxidative properties using a FRAP method. The fruits and leaves of the American cranberry were characterized by a high content of polyphenolic compounds and by an antioxidative potential, and the anatomical part of this plant contributed to both the total content of polyphenols and to their profile, as well as to the activity towards ferric ions. The leaves of Vaccinium macrocarpon L had the highest amount of bioactive compounds; however, compared to the fruits, the type of polyphenols contained therein impacted their reducing potential to a lower extent. Considering the significant content of health-promoting compounds, it could be possible to use not only the American cranberry fruits, but, also, its leaves when developing new food products (for example smoothies, functional drinks).