Sm³⁺-doped BaMoO₄ phosphor thin films were prepared by radio-frequency magnetron sputtering on sapphire substrates at several growth temperatures followed by rapid thermal annealing. A 1 inch-diameter BaMoO₄ target doped with 5 mol% Sm₂O₃ was synthesized using solid-state reaction of BaCO₃, MoO₃, and Sm₂O₃ as starting materials. The highest red emission intensity of BaMoO₄:Sm³⁺ phosphor thin film was achieved at a growth temperature of 400 °C, where the optical band gap was 4.70 eV and the color chromaticity coordinate was (0.492, 0.353). These results suggest that the BaMoO₄:Sm³⁺ phosphor thin film is a promising candidate for application in red-light-emitting devices.