Polyblends of poly(butylene terephthalate) (PBT) with four different types of co[poly(ethylene terephthalate-p-oxybenzoate)] copolyester, designated as P28, P46, P64, and P82, were prepared by melt-blending. The crystallization behaviors of the blends were then studied by differential scanning calorimetry and polarized optical microscopy (POM). Crystallization rate and temperature of neat PBT are increased when less than 10 wt % of P28 is blended. On the contrary, crystallization rate and temperature of neat PBT decrease when 10 wt % of P46, P64, or P82 copolyesters is blended. The crystallization behaviors of the blends are confirmed by the POM observations at the cooling cycles of the melts. On the other hand, melting endotherm onset temperature and melting peak width for all blends are comparable with those of neat PBT. These results imply that the stability and distribution of PBT crystallites in the blends are not significantly influenced by blending. The effects of POB content in the composition of the blends on the crystalline morphology were also presented. It is found that the structure of crystallites of the blends changed gradually with increasing the POB content in the composition of copolyester from lamellar to cross-like spherulite structures.