We investigate the reinforcing effects of both unmodified and surface modified nano titanium dioxide (TiO2) on the cure, mechanical, and thermal properties of natural rubber (NR) nanocomposites. The surface of nano TiO2 is modified by cationic surfactants cetyltrimethylammonium bromide (CTAB) and tetraethylammonium bromide (TEAB). The surface modification of nano TiO2 is characterized by Fourier transform infrared (FTIR) spectra and Field emission scanning electron microscopy (FESEM). The result reveals that surface modified nano TiO2 is much more efficient in improving the resulting properties of NR nanocomposites in comparison with unmodified nano TiO2. The excellent improvement in the properties of surface modified nano TiO2/NR composites is due to the better hydrophobicity and uniform dispersion of modified nano TiO2 within the NR matrix, as confirmed from morphological analysis. CTAB is much more effective than TEAB with respect to the properties of nano TiO2 based NR composites.