This article provided a convenient method to synthesize aliphatic polyesteramides mainly composed of alternating diester diamide units by polycondensation and chain extension. Two kinds of polyesteramide prepolymers were prepared through melt polycondensation from N,N'-bis(2-hydroxyethyl)oxamide and adipic acid or sebacic acid. Chain extension of them was conducted with 2,2-(1,4-phenylene)-bis(2-oxazoline) and adipoyl biscaprolactamate as combined chain extenders. The chain extended polyesteramides (ExtPEAs) were characterized by IR, H-1 NMR, differential scanning calorimetry, thermogravimetric analysis, wide-angle X-ray scattering, tensile test, and dynamic thermomechanical analysis. The results showed that the ExtPEA(0, m)s were mainly constituted with the diester oxamide alternating units. They had T-m above 140.8 degrees C and the initial decomposition temperature above 298.0 degrees C. They crystallized in similar crystallites to Nylon-66 and were thermoplastic materials with tensile strength up to 31.47 MPa. POLYM. ENG. SCI., 54:756-765, 2014. (c) 2013 Society of Plastics Engineers