Summary: The crystallization behavior of a poly(butylene succinate)‐based ionomer (PBSi) was analyzed by morphological observations and synchrotron small‐angle X‐ray scattering (SAXS) experiments. The spherulitic morphology of PBSi is composed of irregular lamellae propagating outwards from the center with ionic clusters isolated from the crystalline lamellae. Synchrotron radiation SAXS profiles revealed that the re‐crystallization during heating process was effectively retarded with increasing ionic content, suggesting that the presence of ion aggregates affects the extent of diffusion of chains towards crystallization.