Sodium titanate nanotubes (NaTiNTs) were prepared by hydrothermal method and functionalized with three different silane coupling agents. The existence of the chemical bond between silane molecules and nanoparticles was confirmed by scanning electron microscopy (SEM) equipped with electron dispersive X-ray spectroscopy (EDS) mapping, Fourier transform infrared (FTIR) spectroscopy, and simultaneous differential scanning calorimetry–thermogravimetric analysis (DSC-TGA). NaTiNTs before and after functionalization were characterized by X-ray diffraction (XRD) technique. Functionalized NaTiNTs were used to prepare epoxy-based nanocomposites with three different wt.% of nanofillers (1, 2, and 3 wt.% per epoxy). The thermal and mechanical properties of prepared nanocomposites were studied by DSC, DSC-TGA, and dynamic mechanical analysis (DMA). The obtained results were compared to the epoxy. The results showed that the glass transition temperature increased from 72 to 79 °C. Storage modulus increased by 10.4% at 3 wt.% nanotubes. From all results appropriate functionalized NaTiNTs were chosen and nanocomposites for determination of combustion properties by cone calorimeter were prepared (1, 3, and 5 wt.% of nanofiller per epoxy). Significant reduction of the heat release rate (HRR) depending on the inorganic particles loading was observed. The peak value for HRR was reduced by about 40% compared to the epoxy, while ignition time and total heat release (THR) are not significantly affected by the presence of the inorganic particles.