Arabinoxylan-catechin complexes were synthesized using two eco-friendly methods: cold plasma and ultrasonic treatments. Their physicochemical, structural and functional properties were evaluated. Cold plasma and ultrasonic treatments did not significantly alter the molecular structure of arabinoxylan, although a decrease Mw was noticed. Grafting ratios increased by elevating ultrasonic power to 200 W for 3 min and cold plasma power to 50 V for 3 min. UV-vis, FT-IR, and SEM analyses revealed the formation of covalent bonds between arabinoxylan and catechin after cold plasma and ultrasonic treatment. Arabinoxylan's viscosity and thermal stability decreased upon catechin mixing. Furthermore, the in vitro antioxidant activities of the cold plasma and ultrasonic samples were significantly enhanced compared with those of the physically mixed sample. This work provides two eco-friendly methods: cold plasma and ultrasonic treatments, which are operationally flexible, chemical-free, and sustainable for the preparation of polysaccharide-polyphenol conjugates, consequently modifying the functional and antioxidant activities of polysaccharides.