Polyoxyethylene–polyamide multiblock copolymers were successfully synthesized from α, ω-polyoxyethylene–dicarboxylic acid (POE–diacid), a mixture of two dicarbroxylic acids, and an aromatic discocynate by two synthetic routes, i.e., one-step and two-step method. In the two-step method, α, ω-diisocyanate-terminated polyamide oligomers, preformed from a mixture of isophthalic acid (IPA) and azelaic acid (AZA) with 4,4′-methylenedi (phenyl isocyanate) (MDI), were reacted with POE–diacid to form multiblock copolymers. In the one-step method, the reaction components, MDI, IPA, AZA, and POE diacid, were reacted all together. These polymerizations were carried out in the presence of 3-methyl-1phenyl-2-phospholene 1-oxide as a catalyst in tetramethylene sulfone, giving multiblock copolymers with inherent viscosities of 0.5–1.1 dL/g. They were soluble in amide-type solvents, and transparent, ductile, and elastomeric films could be cast from their N,N-dimethylacetamide solutions. The tensile strength and modulus of the films thus prepared decreased with an increase in the polyoxyethylene content, whereas the elongation at break increased. The tensile strength/elongation at break/tensile modulus of the multiblock copolymer films ranged from 47 MPa/160%/1.1 GPa to 15 MPa/880%/12 MPa.