Thermal degradation of poly(vinyl chloride) was studied in a nitrogen atmosphere in the presence of Jatropha seed oil, epoxidized Jatropha seed oil, and soaps (barium and cadmium) of Jatropha seed oil at various temperatures. The rate of dehydrochlorination measurement at 1% degradation, R(DH), and the time required for dehydrochlorination to attain 1% conversion were used to assess the effect of the additives on the susceptibility of the polymer to dehydrochlorination. It was found from the kinetic studies and the results from viscosity measurements on degraded polymer samples that the Jatropha seed oil derivatives suppressed the initial loss of HCl from the polymer and the extent of polymer chain scission accompanying the dehydrochlorination process. Thermal degradation studies of poly(vinyl chloride) in the presence of mixtures of barium and cadmium soaps of Jatropha seed oil were also carried out. It was found that soap mixtures containing less than 80 wt % cadmium soap exerted a deleterious (antagonistic) effect on the degradation of poly(vinyl chloride) while in the presence of soaps containing more than 80 wt % cadmium soap, considerably lower values of R(DH) and higher values of t(DH) were observed. The soap mixture containing 90 wt % cadmium soap was found to exhibit a remarkedly improved stabilizing effect on the dehydrochlorination of poly(vinyl chloride).