Thulium ions (Tm3+) are employed to expand the luminescent properties of metal halide perovskites due to their rich array of long-wavelength near-infrared (NIR) luminescent energy levels. However, Tm3+ still exhibits weak emission in double perovskites (DPs) owing to the parity-forbidden nature of its f–f transitions, leading to poor absorption. In this study, the rare-earth-based DP Cs2NaTmCl6 was successfully synthesized via a facile method. This material exhibits self-sensitized NIR-I and NIR-II emission under its characteristic excitation. Upon introducing Sb3+ ions, which possess strong absorption in the UV region, the NIR photoluminescence external quantum efficiency (EQE) of Cs2NaTmCl6:3% Sb3+ reaches 21.6%. This enhancement is attributed to the presence of the 1G4 energy level of Tm3+, which acts as a bridge to efficiently transfer energy from the high-energy states of Sb3+ to the NIR-emitting states of Tm3+. Both the pristine and Sb3+-doped Cs2NaTmCl6 demonstrate excellent thermal quenching resistance. Through a combined experimental and theoretical approach, we demonstrate that the incorporation of Sb3+ ions reduces the effective optical bandgap of the host matrix by providing additional absorption channels. Leveraging the efficient NIR luminescence, we designed an NIR night-vision illumination and imaging system. Furthermore, exploiting the emergence of visible luminescence and the distinct NIR emission intensities before and after Sb3+ doping, we developed a dual-mode optical anti-counterfeiting label. These findings provide novel design insights and inspiration for achieving NIR luminescence in rare-earth-based DPs.