Ag+for Sm3+substitution in the scheelite-type AgxSm(2–x)/3□(1–2x)/3WO4tungstates has been investigated for its influence on the cation-vacancy ordering and luminescence properties. A solid state method was used to synthesize the x= 0.286 and x= 0.2 compounds, which exhibited (3 + 1)D incommensurately modulated structures in the transmission electron microscopy study. Their structures were refined using high resolution synchrotron powder X-ray diffraction data. Under near-ultraviolet light, both compounds show the characteristic emission lines for 4G5/2→ 6HJ(J= 5/2, 7/2, 9/2, and 11/2) transitions of the Sm3+ions in the range 550–720 nm, with the J= 9/2 transition at the ∼648 nm region being dominant for all photoluminescence spectra. The intensities of the 4G5/2→ 6H9/2and 4G5/2→ 6H7/2bands have different temperature dependencies. The emission intensity ratios (R) for these bands vary reproducibly with temperature, allowing the use of these materials as thermographic phosphors.