Miscibility, crystallization behavior, crystal structure, and microstructure of biodegradable poly(butylene succinate)/tannic acid (PBSU/TA) blends were studied with differential scanning calorimetry, optical microscopy, wide-angle X-ray diffraction, and small-angle X-ray scattering in this work. PBSU and TA are miscible as evidenced by the single composition dependent glass transition temperature over the whole blend composition range and the depression of equilibrium melting point of PBSU in the blends. Nonisothermal melt crystallization of PBSU is retarded by the presence of TA. It is found that blending with TA affects the spherulitic morphology of PBSU apparently but does not modify the crystal structure of PBSU. The long period and thickness of the amorphous phase become larger with increasing the TA content in the blends, indicating that TA mainly resides in the interlamellar region of PBSU spherulites.