In this work, nanocomposites with a high thermal stability were developed using T-DDM, a new benzoxazine resin based on 4,4’-diaminodiphenylmethane (DDM) and tyrosol, and zinc oxide (ZnO) nanoparticles. Thermal analysis allowed to determine some kinetic parameters such as the activation energy and reaction order relative to the ring-opening polymerisation (ROP) of the resin. Then, a synergetic effect of the ZnO nanoparticles on the ROP’s enthalpy was evidenced, and a significant improvement of the degradation temperature and char yield was found. The interaction between the benzoxazine matrix and the ZnO nanoparticles was further investigated by FTIR spectroscopy.