Herein, we developed a straightforward aqueous synthesis of unprecedented alternating peptide-peptoid copolymers via a Ugi four-component reaction applied to dipeptides. Functional peptide-peptoid copolymers as well as block copolymers were produced in a single step in the presence of acrylic acid and carboxylic acid-terminated poly(ethylene glycol). The thermoresponsiveness of these polymers is highlighted.