Sustainable polybenzoxazines sourced from renewable feedstock has emerged as an area of interest due to the inherent presence of a high number of reactive and additional functionalities. Plants are a rich source of flavan-3-ol viz., catechin (CAT) with four phenolic-OH and one aliphatic secondary-OH that can be a viable substitute to petro-phenols. In this current work, a biobased benzoxazine monomer, viz. CAT-fa, is synthesized using CAT and carbohydrate sourced furfurylamine (fa). Interestingly, an unexpected tris-oxazine (instead of tetra-oxazine) benzoxazine monomer is obtained. The unreacted phenolic-OH is involved in intramolecular H-bonding with the neighboring oxazine ring. Upon heat treatment, H-bonded hydroxyl groups become free and initiate ring-opening polymerization reaction at a low temperature of ≈125 °C exhibiting the latent catalyst effect. The ring-opening polymerization of the monomer and the thermal stability of polybenzoxazine are analyzed by differential scanning calorimetry, thermal gravimetric analysis, rheometry, and Fourier transform infrared spectroscopy. The polymerization reaction is proposed to proceed by the ring-opening reaction by cleavage at the oxygen of the pyran ring and O─CH2-N bond in oxazine ring to generate multiple polar functionalities to enable extensive H-bonding interactions. This work supports the potential of catechin as a green synthon to form sustainable polymers to employ H-bonding interactions and latent-catalytic potential. © 2022 Wiley-VCH GmbH.