The main objective of this work is to reveal a newly developed synthesis procedure for mesoporous-assembled SrTiO3 nanocrystal photocatalyst using a sol–gel process combined with structure-directing surfactant. The obtained photocatalyst exhibited much higher photocatalytic activity for degradation of methyl orange, used as a model azo dye pollutant in wastewater, than commercially available SrTiO3 nanopowder.