Hierarchically assembled TiO 2 nanoparticles into larger spherical ones were obtained using aerosol-assisted processing method. Unagglomerated particles with the mean size of 440 nm were obtained from colloidal solution of TiO 2 nanoparticles (~4.5 nm) using ultrasonic spray pyrolysis at 550°C. Their morphological complexity and structural polymorphism were investigated by using X-ray powder diffraction (XRPD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM) coupled with selected area electron diffraction (SAED) analysis. Pronounced evolution of nanocrystalline TiO 2 (B) phase assembled together with the anatase building units (sized ~ 15 nm) in uniform submicrometric particles implicate their feasibility to be used in dye-sensitised solar cells and lithium ion batteries.