In this study, we investigated the effects of mesoporous titanium silicate (TS-1) zeolite on the melting behavior and isothermal crystallization in poly(butylene succinate) (PBS)/TS-1 zeolite hybrid composites (PTHC). Isothermal crystallization results revealed that TS-1 zeolite acted as a nucleation agent in PTHC, thus the $t_{1/2}$ of PTHC was faster than that of homo-PBS. However, the nucleation effect of TS-1zeolite did not depend on the TS-1 zeolite content. The large surface area of the mesoporous structure readily formed molecular chains inside and outside of the pore mouths of TS-1 zeolite, covering the nucleation site, as a result of the byproduct deposition during polymerization. At isothermal crystallization, temperatures ranging from 88 to $92^{circ}C$, nucleation of TS-1 zeolite occurred because of the presence of free byproducts and the formation of a molecular chain in the pore mouths. In contrast, isothermal temperatures ranging from 80 to $84^{circ}C$ resulted in ineffective nucleus activation because of the steric hindrance in the porous structure. Synchrotron small-angle X-ray scattering (SAXS) analysis revealed that TS-1 zeolite can accelerate lamellar recrystallization during heating.