The water-extractable (QWP) and the alkali-extractable (QAP) polysaccharides from quinoa (named QWP and QAP, respectively) and their four polysaccharide sub-fractions (QWP-1, QWP-2, QAP-1 and QAP-2), were isolated and purified by anion-exchange and gel filtration chromatography. QWP-1 and QWP-2 were composed of Rha, Ara, Gal and GalA. QAP-1 and QAP-2 were composed of Rha, Ara, Man, Gal and GalA. Antioxidant and immunoregulatory activities of the polysaccharides were evaluated. The results showed that QWP-1, QWP-2, QAP-1 and QAP-2 had significant antioxidant and immunoregulatory activities. The results suggest that QWP-1, QWP-2, QAP-1 and QAP-2 could be used as potential antioxidants and immunomodulators.