A series of SrY2(MoO4)4 phosphors doped and co-doped with Tb3+/Sm3+ ions was synthesized to develop new optical temperature sensor materials. The structures, morphologies, and luminescent characteristics of these phosphors were thoroughly investigated. Luminescence spectra of mono-doped SrY2(MoO4)4 phosphors were measured under the excitation at 375 and 403 nm corresponding to direct excitation of Tb3+ and Sm3+, respectively. The characteristic luminescence bands corresponding to electronic transitions of terbium and samarium ions were detected and investigated for different dopant concentrations. The emission spectrum of the Tb3+/Sm3+ co-doped sample exhibited a total of five distinct emission peaks, indicating an energy transfer from Tb3+ to Sm3+ ions. The energy transfer efficiency from Tb3+ ions to Sm3+ ions was investigated in detail. At elevated temperatures, Tb3+ and Sm3+ exhibited distinct thermal sensitivities in their emission and excitation spectra, leading to evident thermochromic behavior. The fluorescence intensity ratio (FIR) was utilized with dual center to evaluate the temperature sensitivity of SrY2(MoO4)4:Tb3+/Sm3+ phosphors. The temperature sensing mechanism relied on the emission band intensity ratios of the 4G5/2 → 6H5/2, 4G5/2 → 6H9/2, and 4G5/2 → 6H7/2 transitions of Sm3+ in conjunction with the 5D5/2 → 7F5/2 transitions of Tb3+. This approach demonstrated high thermal sensitivity values, reaching up to 0.9% K-1. The studied nanoparticles exhibited sub-degree thermal resolution, making them suitable candidates for precise temperature-sensing applications.