<p>A series of novel red-emitting Na₃LaW₃O₁₂: <i>x</i>Sm³⁺ (<i>x</i> = 0–0.1) and Na₃LaW₃O₁₂: 0.06Sm³⁺, <i>y</i>Eu³⁺ (<i>y</i> = 0.09–0.27) phosphors have been synthesized through a high-temperature solid-state method. The phase structure, luminescent properties, and thermal stability of these materials were analyzed by the X-ray diffraction, scanning electron microcopy, luminescence spectra, luminescence decay curves, and temperature-dependent spectra. The Na₃LaW₃O₁₂: Sm³⁺, Eu³⁺ phosphor show an abnormal thermal stability property, and the luminescence intensity of Na₃LaW₃O₁₂: 0.06Sm³⁺, 0.21Eu³⁺ at 453&#xa0;K remains about 97% of the original value at room temperature. Based on the as-synthesized Na₃LaW₃O₁₂: 0.06Sm³⁺, 0.21Eu³⁺ phosphors as red component, a white LED with 2653&#xa0;K correlated color temperature and <i>R</i>_a = 85.0 color rendering index has been fabricated using a 465&#xa0;nm blue chip, and LuAG: Ce³⁺ yellowish-green phosphor. The results indicated that the as-synthesized Na₃LaW₃O₁₂: Sm³⁺, Eu³⁺ phosphor may be applied in white LEDs as potential abnormal thermal quenching red-emitting material.</p>