A mesoporous assembly of layered titanate with well-dispersed Pt cocatalysts has been synthesized via a restacking of exfoliated titanate nanosheets and a simultaneous adsorption of Pt nanoparticles. According to powder X-ray diffraction analysis, the obtained mesoporous assembly shows amorphous structure corresponding to the disordered stacking of layered titanate crystallites. Field emission-scanning electron microscopy and $N_2$ adsorption-desorption isotherm measurement clearly demonstrate the formation of mesoporous structure with expanded surface area due to the house-of-cards type stacking of the titanate crystallites. From high resolution-transmission electron microscopy and elemental mapping analyses, it is found that Pt nanoparticles with the size of ~2.5 nm are homogeneously dispersed in the mesoporous assembly of layered titanate. In comparison with the protonated titanate, the present mesoporous assembly of layered titanate exhibits better photocatalytic activity for the photodegradation of organic molecules. This finding underscores that the restacking of exfoliated nanosheets is quite useful not only in creating mesoporous structure but also in improving the photocatalytic activity of titanium oxide.