In this article, a new synthetic approach for the modification of partial glycerides (PG) obtained from sunflower oil with thermally curable benzoxazine units and its potential use as a coating material are described. For this purpose, hydroxyl-containing benzoxazine monomer was first prepared by conventional ring-forming reaction of phenol with paraformaldehyde in the presence of 6-amino-1-hexanol. The subsequent urethane reaction between PG and the benzoxazine monomer using toluene diisocyanate yields corresponding modified oil. The structures of the intermediates, and the modified triglycerides are confirmed by FTIR and H-1 NMR spectral analysis. Thermally activated curing behaviors of the precursor and the modified oil in the absence of any catalyst were studied by differential scanning calorimetry. Thermal and film properties of the cured products were also investigated.