Synthesis of nanoporous TiO2 particles using an ionic liquid (IL)-assisted sol-gel method was investigated. The TiO2 particles prepared using a water-immiscible room-temperature ionic liquid, [Bmim][PF6], as an effective templating material showed good structural properties including high surface area, stable crystal structure, controlled porosity and tailor-designed pore size distribution. Due to the unique properties of the ionic liquid including near-zero vapor pressure and water-immiscibility, TiO2 particles with the anatase crystal phase were formed after the extraction of organic solvents without further heat treatment at high temperature. It was revealed that the strength of the hydrogen bonds in the anionic part of the ionic liquid to water was an essential factor to form this porous structure of TiO2 particles. The mechanism forming these nanostructured particles seemed to follow the effective aggregation of TiO2 particles with a self-assembled ionic liquid. Moreover, the length of alkyl group in the cationic part of the ionic liquid could determine the pore size and the pore volume of TiO2 particles. Among the ionic liquids tested, it was found that 1-buthyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) was the most effective to prepare well-structured mesoporous TiO2 particles.