Accurate models of epoxy resin cure reactions are essential for intelligent processing of polymer matrix composites. In this study, two model systems for epoxy-amine reactions, phenyl glycidyl ether with aniline and with m-phenylenediamine, were studied via in situ near-infrared spectroscopy. The quality of the near-IR spectra enables concentrations of individual chemical species to be obtained in real time. A mechanistic model was proposed, and the corresponding kinetic parameters were evaluated. Excellent agreement was observed between the proposed mechanistic model and the experimental results. Substitution effects were found insignificant with both systems studied.