The curing kinetics of the modified triglycidyl isocyanurate (TGIC) with various content of N-phenylmaleimido group and carboxylated polyester (CPE) was investigated using dynamic differential scanning calorimetry (DSC). The curing kinetic behavior was well described by Šesták–Berggren (SB (m, n)) model. The m order of the curing reaction was varied from 0.229 to 0.356 and n order varied from 1.278 to 2.035, depending on the PMI content. In addition, the isoconversional method of Kissinger–Akahira–Sunose (KAS) was applied to correlate the activation energy (Ea) with the extent of cure. The obtained Ea increased with increasing phenyl maleimide content. As α increases, Ea declined up to α≈0.3, then remained almost constant for α≈0.3–0.8, and finally increased until completion of reaction, indicating complex reaction mechanism. The thermal stability of the cured modified TGIC/CPE was enhanced with incorporation of phenyl maleimide.