The structural and photoluminescence properties of Eu³⁺-doped Y₂Sn₂O₇ nanoparticles have been systematicallystudied as a function of heat treatment temperature. Crystalline Y₂Sn₂O₇:Eu nanoparticles with sizes in the range of 2–5 nm were prepared at the relatively low temperature of 700 °C. Based on the Rietveld refinement of powder X-ray diffraction patterns, it was confirmed that the YO₈/EuO₈ polyhedra in the Y₂Sn₂O₇:Eu lattice become more symmetric as the annealing temperature increases. The extent of distortion of the YO₈/EuO₈ polyhedra is reflected in the luminescence parameters Ω₂ and Ω₄, which are a measure of the polarizability of Y–O and Eu–O bonds in the lattice. There are a significant number of surface Eu³⁺ ions in the nanoparticles annealed at 700 °C and the emission intensities of the Eu³⁺ ions in the nanoparticles are mainly decided by the surface Eu³⁺ ions, the concentration of which decreases with increasing temperature. Incorporation of the nanoparticles in a poly- (methyl methacrylate) (PMMA) matrix leads to a decrease in the ⁵D₀ lifetime and this has been attributed to the quenching of the excited states of surface Eu³⁺ ions through the vibrations of different structural units in PMMA.