In this study, diisononyl phthalate (DINP), a conventional plasticizer of poly(vinyl chloride) (PVC), was partially replaced by a polymeric plasticizer, poly(butylene succinate) (PBS), in order to reduce the leaching out of lowmolecular-weight plasticizer from the plasticized PVC. Samples were prepared by melt mixing on a two-roll mill followed by compression molding into a 3-mm thick sheet. The DINP/PBS-plasticized PVC provides a dosedependent increase in the tensile properties (tensile strength, Young's modulus, and elongation at break), tear strength, and thermal stability, as compared with the DINP-plasticized PVC. According to the overall properties, PVC plasticized with 10/30 phr (parts by weight per hundred parts of resin) DINP/PBS was selected for preparing composites with varied loadings of an ultrafine wollastonite (particle size of 1,200 mesh). Their tensile properties, tear strength, thermal stability, and morphology were evaluated and compared with the 40 phr of DINP-plasticized PVC composites. The results showed an increase in the Young's modulus and thermal stability but a decrease in the tensile strength, elongation at break, and tear strength of either 40 phr of DINP-or 10/30 phr of DINP/PBS-plasticized PVC composites. Therefore, the products may be useful where the dimensional and thermal stability of the plasticized PVC are needed. J. VINYL ADDIT. TECHNOL., 21:220-227, 2015.