This study was undertaken to examine possible use of classic tetravalent tin-based heat stabilizers for the preparation of a polymer plasticizer: poly(ε-caprolactone) (PCL) and simultaneous stabilization of PVC in PVC/PCL mixtures. PCL was prepared from ε-caprolactone (CL) by polymerization initiated by tin-containing organic compounds and successfully used to simultaneously plasticize and stabilize PVC. Moreover, conditions under which the polymerization of CL took place directly in situ during PVC/CL mixture processing were found. The procedure yielded homogeneous plasticized PVC/PCL mixtures, which were stable and contained >90% of the original monomer content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41066.