We describe the fabrication of thermally conductive composites based on a thermoplastic polyurethane (TPU) matrix by hybrid surface treatment with hexagonal boron nitride (h-BN) via the melt mixing method. BN particles were surface-treated with amino propyl triethoxysilane (APTES) and aniline trimer (AT). For the same weight content of BN, BN composites surface-treated with AT showed better mechanical strength and thermal conductivity than those surface-treated with APTES. because of the intercalation of the AT between BN and TPU, which not only increased the wettability but also provided a good heat transfer path. The composites fabricated by our melt mixing process endured approximately 200,000 bending cycles without rupturing or decreasing the thermal conductivity. Furthermore, even after bending tests, the APTES/AT/BN-based composites exhibited the best mechanical and thermal properties.