Biodegradable multiblock copolymers poly(butylene succinate-b-poly(ethylene glycol) succinate) P(BS-b-PEGS)) were prepared by direct polycondensation. The thermal and crystallization behavior of P(BS-b-PEGS) with weight fraction of PEGS component from 6 to 26 wt % were comparatively investigated with those of neat poly(butylene succinate) (PBS) by wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and polarized optical microscopy (POM). P(BS-b-PEGS) showed the same crystal structure as neat PBS, but the degree of crystallinity of copolymers was lower than that of neat PBS and decreased with increase in PEGS content. The isothermal crystallization kinetics study suggests that incorporation of PEGS component did not change the crystallization mechanism, but reduced the crystallization rate of the samples, and that increasing crystallization temperature decreased the crystallization rate of all the samples. The spherulites of neat PBS and P(BS-b-PEGS) showed banded morphologies. The spherulitic growth rate of the samples also decreased with increase of PEGS content and crystallization temperature. A transition from crystallization regime II to III occurred for all the samples, and the transition shifted to lower temperatures with increase in PEGS content.