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A series of Eu3+ doped Sr2GdTaO6 (SGT) phosphors with double perovskite structure were synthesized via a high-temperature solid-state reaction approach. The crystal structure, morphology and luminescence properties were characterized by means of X-ray diffraction, transmission electron microscope, luminescence spectroscopy and fluorescence decay lifetimes, respectively. Under the excitation of 394 nm, intense red emission in the visible region was observed in Eu3+ doped SGT phosphors, and the critical quenching concentration of Eu3+ in SGT phosphors was derived to be 15 mol%. The chromaticity coordinates and color purity of SGT: 15 mol% Eu3+ were calculated to be (0.61, 0.36) an 93.82 %, respectively. Meanwhile, it was also confirmed that the electric quadrupole–quadrupole interaction is responsible for the luminescence concentration quenching of Eu3+. The internal quantum efficiency of SGT: Eu3+ phosphors with different Eu3+ concentrations were calculated. Furthermore, the crossover process was confirmed to be the main mechanism for luminescence thermal quenching based on the temperature-dependent emission spectra and temperature-dependent fluorescence lifetimes. In addition, the Judd-Ofelt parameters, radiative transition rates and branch ratios from the 5D0 emitting states to various lower energy states were evaluated with the aid of the Judd-Ofelt theory, respectively. All results indicate that SGT: Eu3+ samples are a promising red-emitting phosphor.