[en] Highlights: • Tung oil was successfully converted into epoxidized dicarboxylic acid dimethyl ester (epoxidized-C21-DAE). • Epoxidized-C21-DAE are introduced as primary plasticizer and auxiliary thermal stabilizer for poly(vinyl chloride)(PVC). • The epoxidized-C21-DAE as a primary plasticizer for PVC significantly improved PVC thermal stability and flexibility. • The epoxidized-C21-DAE plasticizer was compatible with PVC and could not be easily extracted A tung oil derived epoxidized dicarboxylic acid dimethyl ester (epoxidized-C21-DAE), was synthesized through transesterification, a Diels-Alder reaction, and epoxidation. The chemical structure of the epoxidized-C21-DAE was confirmed using Fourier transform infrared spectroscopy (FTIR), proton nuclear magnetic resonance (¹H NMR) and carbon-13 nuclear magnetic resonance (¹³C NMR). The thermal and migration stabilities and the mechanical properties of PVC samples were investigated using discoloration, tensile, exudation, volatility, and extraction tests as well as thermal gravity analysis (TGA), TGA–FTIR analysis, and dynamic mechanical analysis (DMA). The petroleum-based plasticizer, dioctyl terephthalate (DOTP), and the biobased plasticizer, epoxidized fatty acid methyl ester (EFAME), were chosen as controls and their properties compared with epoxidized-C21-DAE. The application of epoxidized C21-DAE as a biobased, primary plasticizer for poly(vinyl chloride) significantly improved PVC thermal stability over that of DOTP and EFAME. The mechanical properties of this type of PVC were superior to those of DOTP. In addition, the migration and volatility stabilities of epoxidized-C21-DAE were much better than EFAME. Epoxidized-C21-DAE could, therefore, be fully substituted for commercial DOTP or EFAME. Tung oil derived epoxidized-C21-DAE has good potential as a primary PVC plasticizer.