<p>Lead-free halide perovskites have emerged as promising scintillators owing to their strong X-ray attenuation and high internal quantum efficiency (IQE). However, the widespread application is hindered by intrinsic moisture sensitivity. Herein, CsSrCl₃:Eu²⁺ nanocrystals are grown <i>in situ</i> in a specially designed inorganic glass matrix. By employing [PO₄]-modification and controlled crystallization strategies, we obtain a transparent CsSrCl₃:Eu²⁺ glass-ceramic (GC) scintillator that combines high crystallinity (15.9%) with excellent optical transparency (85.3% at 432 nm). CsSrCl₃:Eu²⁺ GC exhibits outstanding photoluminescence (PL) performances, including the high IQE of 87.6% and superior thermal stability (74% intensity retention at 493 K relative to 303 K). Benefiting from effective protection by the robust glass matrix, CsSrCl₃:Eu²⁺ GC retains 99% of the initial PL intensity after 14 days of water immersion. Under X-ray excitation, CsSrCl₃:Eu²⁺ GC exhibits blue X-ray excited luminescence (XEL), with XEL peak intensity and integrated XEL intensity reaching 117% and 25.1% of those of the Bi₄Ge₃O₁₂ crystal, respectively. The scintillator achieves a high X-ray imaging spatial resolution of 20 lp mm⁻¹. Furthermore, CsSrCl₃:Eu²⁺ GC demonstrates exceptional operational stability in humid environments, maintaining clear X-ray image contrast even after 48 h of submersion in water. This study not only provides an effective strategy for stabilizing hygroscopic halide scintillators in a durable [PO₄]-modified fluoroaluminate glass matrix but also demonstrates the great potential of CsSrCl₃: Eu²⁺ GC for high-resolution and stable X-ray imaging.</p>