Enhancing the thermal stability of plasticized PVC is a critically important task for expanding its practical application areas. The development of eco-friendly modifying additives is a promising direction in this field. Titanium phosphates meet the requirements of green chemistry, and their use in the form of hierarchical microstructured materials contributes to improving material characteristics. Complex esters of adipic acid are widely used as alternative PVC plasticizers that promote increased thermal stability. This study investigates the combined effect of titanium phosphates and diphenoxyethyladipinate on the thermal characteristics of PVC. The thermal stability of PVC compositions was studied using Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) in an oxidative environment (air). The obtained results show an improvement in the thermal characteristics of the compositions compared to the base PVC compound plasticized with dioctyl phthalate (DOP). The key evaluation parameters for the composition are as follows: initial mass loss temperature (Tₒₙ); coke residue; temperature of maximum decomposition rate (Tmax DTG); and temperature of maximum heat flow (Tmax DSC) during the main stage of thermolysis. Increasing the DFEA (diphenoxyethyladipinate) content in the PVC composition from 16 to 49 parts by weight demonstrated improved thermal characteristics. The initial temperature of the sample mass loss indicated a shift of the degradation process towards higher temperatures. The shift in the maximum of the first stage of PVC composition degradation—dehydrochlorination—confirmed a reduction in the rate of thermal degradation of the material. Analysis of DSC data confirmed an increase in the thermal stability of the composition, expressed in an increase in the Tmax DSC value. A PVC composition with improved thermoanalytical characteristics using eco-friendly additives was developed.