Chenopodium quinoa Willd. is an ancient food crop that has provided nutrition to Andean populations for thousands of years. BRS Piabiru is a quinoa genotype developed and adapted to tropical climate by the Brazilian Agricultural Research Corporation. In this work, BRS Piabiru quinoa was evaluated concerning its nutritional, physicochemical and phenolic composition and also its bioactive properties. This variety showed high carbohydrate and protein contents and a low-fat level, composed of 86% of unsaturated fatty acids, 60% of which are polyunsaturated fatty acids. Four organic acids were detected, with quinic acid as the most abundant, while α- and γ-tocopherols were the vitamin E isoforms found. Quercetin and kaempferol glycosides were the main phenolic compounds in the quinoa extract, which also revealed relevant antioxidant and antimicrobial activities, with no toxic effect. These results support the potential of BRS Piabiru quinoa as a nutritious food crop and a source of bioactive compounds.