Two-dimensional (2D) transition metal dichalcogenides (TMDCs), due to their unique physical properties, have a wide range of applications in the next generation of electronics, optoelectronics, and valleytronics. Large-scale preparation of high-quality TMDCs films is critical to realize these potential applications. Here we report a study on metal-organic chemical vapor deposition (MOCVD) growth of wafer-scale MoSe₂ films guided by the crystalline step edges of miscut sapphire wafers. We established that the nucleation density and growth rate of MoSe₂ films were positively correlated with the step-edge density and negatively with the growth temperature. At a certain temperature, the MoSe₂ domains on the substrate with high step-edge density grow faster than that with low density. As a result, wafer-scale and continuous MoSe₂ films can be formed in a short duration (30 min). The MoSe₂ films are of high crystalline quality, as confirmed by systematic Raman and photoluminescence (PL) measurements. The results provide an important methodology for the rapid growth of wafer-scale TMDCs, which may promote the application of 2D semiconductors.