Epoxidized corn oil (ECO) was synthesized and used as reactive diluent for diglycidyl ether of bisphenol A (DGEBA)/Diels-Alder adducts of rosin acids with acrylic acid (AcAAbA) mixtures. The influences of ECO amount on the curing kinetics and thermal properties of cured DGEBA/ECO/AcAAbA mixtures were investigated. From scanning electron microscopy images, a uniform distribution of ECO in the composite structure can be observed. The kinetic analysis of the curing reactions was evaluated, using the variable peak exotherm methods of Flynn-Wall-Ozawa, Kissinger, and the Netzsch Thermokinetics software. The cross-linking reactions were identified to take place in four steps. Kinetic analysis of the thermal degradation of the DGEBA/ECO/AcAAbA was evaluated with the Netzsch Thermokinetics software and occurs in three steps, depending on the chemical structure of the sample. On the basis of the analysis of evolved gases by thermal decomposition coupled with Fourier transform infrared and mass spectrometry techniques, a schematic mechanism for the thermal degradation process was proposed.