Poly(ether-ester-amide)s (PEEAs) based on poly(tetramethylene oxide) and tetra-amide segments were synthesized by a solution/melt polymerization. The tetra-amide segments (T6A6T) were based on adipic acid (A), terephthalic acid (T), and hexamethylene diamine (6), and were synthesized prior to the polymerization. Monodisperse tetra-amide segments, i.e. T6A6T, as well as polydisperse segments, consisting of a mixture of uniform segments of diamide (T6T), tetra-amide (T6A6T), and hexa-amide (T6A6A6T), were utilized in the preparation of the PEEAs. In this way, a polydispersity index ranging from 1.0 to 1.09 could be obtained. In addition, a random copolymer, synthesized by a one-pot polymerization, was also studied and the copolymer had a polydispersity of 1.2. The low polydispersity of the one-pot synthesis amide segments was mainly due to the uneven reactivity of the terephthalic ester groups. The properties of copolymers were studied by DSC, FTIR, DMTA, compression set, and tensile set measurements. When the polydispersity of the amide segments was increased, the copolymers displayed a slower crystallization, a lower final crystallinity, a broader melting transition, a decreased storage modulus at room temperature, as well as a decreased yield strength and inferior elastic properties.