A facile hydrothermal route for the synthesis of h-MoO₃ nanorods and h-/α-MoO₃ composites was proposed. XRD, TG-DSC, FESEM-EDX, TEM, FT-IR, Raman, photoluminescence (PL) and UV-vis DRS spectroscopy were used to characterize the as-synthesized products. h-MoO₃ was formed when the liquid/solid ratio of the raw materials was 2:1 and 5:1. However, homogeneous h-/α-MoO₃ composites were obtained when the liquid/solid ratio was increased to 8:1 and 12:1. A possible mechanism by which h-MoO₃ is formed, and its transformation into α-MoO₃ were investigated. h-MoO₃ annealing was found to comprise three mass-loss stages; i.e., the removal of each of the following: physically adsorbed water, residual ammonium, and coordinated water. Both h-MoO₃ nanorods and h-/α-MoO₃ composites demonstrated excellent visible-light-driven photocatalytic performance with regard to methylene blue degradation. The superior degradation efficiency of the h-/α-MoO₃ composites was ascribed to a lower recombination rate of electron-hole pairs, a reduced band gap energy, and an enhanced synergistic effect.