This study presents a facile approach for the preparation of MoS2 nanosheet decorated by porous titanium dioxide with effective photocatalytic activity. Mesoporous titanium dioxide nanostructures first synthesized by a hydrothermal process using titanium (III) chloride and then the MoS2/TiO2 were prepared through mixing of MoS2 nanosheet with mesoporous titanium dioxide under ultrasonic irradiation. The synthesized nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) analysis. The results showed that the nanocomposite has mesoporous structure with specific surface area of 176.4 m2/g and pore diameter of 20 nm. The as-prepared MoS2/TiO2 nanocomposites exhibited outstanding photocatalytic activity for dye degradation under sunlight irradiation, which could be attributed to synergistic effect between the molybdenum disulfide nanosheet and mesoporous titanium dioxide. The photocatalytic performance achieved is about 2.2 times higher than that of mesoporous TiO2 alone. It is believed that the extended light absorption ability and the large specific surface area of the 2D MoS2 nanosheets in the nanocomposite, leading to the enhanced photocatalytic degradation activity.