Background Quinoa seeds are an excellent source of nutrients and phytochemical compounds with well documented activity; however, different cultivars are usually characterized by different physical properties and chemical composition. This study presented the physical properties, nutrient content, and antioxidant capacities of 25 cultivars of yellow-coated quinoa. Results The results demonstrated that quinoa seeds may be an excellent source of dietary fiber (up to 198 g kg−1 d.m. – Baer cultivar), with a 1:2 ratio of the soluble to insoluble fraction. Digestible carbohydrates were present at the highest level in the Puno cultivar (640 g kg−1). The highest content of proteins was determined in the Colorado 407D and Faro cultivars (c.a. 16%). The average content of albumin and globulins in the seeds was 29.2 and 65.6 g kg−1, respectively. The quinoa seeds were characterized by low activity of protease inhibitors. The lowest inhibition of trypsin was determined for the UDEC-3, Faro Orange, and Titicaca cultivars, and the highest value was exhibited by the Titicaca White and UDEC-5 cultivars. Phenolics in the tested cultivars ranged from 7.1 g kg−1 (UDEC-3) to 10.6 g kg−1 (Temuko). The best antiradical properties were determined for Temuco and Rainbow (2.05 g TE kg−1 and 1.85 g TE kg−1, respectively), while the Baer and Temuco cultivars were characterized by the highest reducing power (2.28 g TE kg−1 and 2.17 g TE kg−1, respectively). Conclusion This study has shown that quinoa cultivated in European countries is a good source of nutrients, dietary fiber, and antioxidants; however, its composition varies significantly. © 2019 Society of Chemical Industry