Titanium dioxide nanoparticles (TiO2 NPs) were synthesized by a facile green method involving TiCl3 hydrolysis with mango-peel extract. The reaction was conducted in an aqueous solution at 80℃ under acidic conditions for 24 h. The samples were characterized using different characterization techniques. The results showed that the crystal structure, size, and crystallinity of TiO2 NPs can be controlled by varying the ratio of the extract to TiCl3. These characteristics and the phase composition (rutile to anatase ratio) of the products decreased with increasing the content of the mango-peel extract in the mixture. Using 5 mg of the extract, the product contained 100% rice-grain-like rutile (28 nm), whereas 100% of anatase spherical nanoparticles (~17 nm) were obtained by incorporating 15 mg of the extract.