The first benzoxazine incorporating cyanate ester group in its structure has been synthesized. The polymerization process investigated by differential scanning calometry (DSC) exhibits two clearly separated exotherm maxima, corresponding to cyanate ester trimerization and benzoxazine, respectively. The nature of each exotherm is studied by Fourier transform infrared spectroscopy (FT-IR). The activation energies for cyanate ester trimerization and benzoxazine ring-opening polymerization are determined by both Kissinger's and Ozawa's methods. Furthermore, both exothermic temperatures observed are lower than those of the published values of benzoxazine and dicyanate ester blends. Thermal properties such as glass transition temperature and char yield are studied by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). Those properties are found to be outstanding compared to the reported properties of general benzoxazine resins and polymerized blends of benzoxazine and dicyanate ester, offering a polymeric matrix for composite satisfying many requirements for such a material.