This work addresses the short-term thermal stability of suspension poly(vinyl chloride) (PVC) films formulated with phosphonium ionic liquids, PhILs (trihexyl(tetradecyl)phosphonium dicyanamide, [P-14,P-6,P-6,P-6][dca]; trihexyl(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide, [P-14,P-6,P-6,P-6] [Tf2N]; tetrabutyl phosphonium chloride, [P-4,P-4,P-4,P-4][Cl]) and their mixtures with a conventional plasticizer (diisononyl phthalate, DINP). Kinetic parameters for the dehydrochlorina-tion step were determined using a well -accepted isoconversional (multi- heating -rate) approach. Results show that PVC films formulated with PhILs, and their mixtures with DINP, present lower thermal stability than those formulated only with DINP, and in spite of PhILs' higher intrinsic thermal stability. Nevertheless, PVC films formulated with [P-14,P-6,P-6,P-6][Tf2N] present the highest long-term thermal stability. Calculated kinetic parameters provide quite good predictions of the thermally stimulated decomposition of most of the targeted formulations. These results are expected to assist on the identification of potential applications of PhILs in the life cycle assessment of PVC-based materials, either as plasticizers/thermal stabilizers or as catalysts for PVC waste recycling processes.