Four novel series of periodic copolymers composed of ester and amide units with the same carbon numbers were synthesized by two-step polycondensation reactions using adipate, linear aliphatic diols, and diamines with various chain lengths, ranging from 3 to 6 methylene groups. Effects of the comonomeric and sequential structures on the physical properties and crystalline structures were investigated for the obtained copolymer series by means of differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), and tensile testing. The thermal properties of obtained periodic copolymer series were found to be strongly dependent on both comonomeric and sequential structures, and the values showed remarkable differences between neighboring methylene numbers in the comonomer units. Such thermal behavior was strongly correlated to the wide-angle X-ray diffraction patterns, with some copolymers displaying patterns similar to homopolyesters, while other copolymers had diffraction patterns that were very different than the homopolyester, dependent on the comonomeric and sequential structures. These results suggest that the molecular chain arrangements and their intermolecular hydrogen bond interactions based on the ester-amide sequential structure play an important role in the formation of a thermally stable crystalline region. Furthermore, the mechanical properties of periodic copolymers were determined from the stress-strain curves of film samples.