Eastern teaberry (Gaultheria procumbens L.) is known for its high content of essential oils in leaves and fruits, which are used in the pharmaceutical, food and cosmetics industries. Recently, teaberries have been attracting more interest owing to their content of polyphenolic compounds. The purpose of our study has been to determine the content of polyphenolic compounds (anthocyanins and total phenols) as well as their antioxidative activity and the concentration of several bioelements (Ca, Mg, Fe and Zn) in extracts from fruits of Eastern teaberry harvested in three different fruit maturity stages. The content of polyphenolic compounds depended on the harvest date. The highest level of these compounds was found in extracts from teaberries collected in the full maturity phase. All teaberry extracts, independently of the harvest date, demonstrated high antioxidative activity. Among the bioelements determined, teaberry extracts contained more calcium than magnesium and more iron than zinc. The content of such bioelements as Mg, Fe and Zn (in contrast to Ca) found in teaberry extracts did not depend on the harvest date.