A novel class of polymeric composite was prepared using benzoxazine polymer (BXP) obtained in an in situ method followed by blending a surface‐functionalized montmorillonite (MMT) clay using 3‐aminopropyltriethoxysilane (APTES). Polymeric matrix used in this study was obtained by mixing bis phenol‐A, aniline and formaldehyde and heating at 150°C. Addition of 7.5 weight % of MMT clay functionalized with APTES formed a composite when heated with the precursors of benzoxazine polymer, forming composites (FeMMT.APTES@BXP3). The structural features of surface‐modified clay, benzoxazine polymer and their composites were confirmed through X‐ray diffraction, Fourier transform infrared, Field Emission Scanning Elecron Microscope (FESEM), Energy Dispersive X‐ray Analysis(EDAX) and elemental mapping studies. Thermal characteristics of the FeMMT.APTES@BXP3 revealed a remarkable thermal stability and retained higher solid mass (63.88%) when subjected to thermogravimetric analysis. Degradation ability of polymer and their composites was also assessed through differential thermogravimetric analysis. Promising hardness features of the polymeric composites were explored by performing Rockwell hardness (RHN) tests. The FeMMT.APTES@BXP3 specimen displayed the RHN as 79 in comparison to all other obtained composites. The composites prepared through this facile method may find remarkable applications in automobile components manufacturing and in high temperature appliances.