Cesium lead halide perovskite (CsPbX 3 ) nanocrystals have intriguing optical and electronic properties, and pressure-induced deformation of [PbX 6 ] octahedra has been employed to regulate their optoelectronic properties. Here, for CsPb(BrI) 3 nanocrystals precipitated in glasses, water quenching is employed to induce the distortion of [PbX 6 ] octahedra and modulate their optical properties. It is found that water quenching results in enlargement of their band gap and formation of extended tail states. Upon subgap excitation, excitons are generated and localized at these distorted [PbX 6 ] octahedra. Transient absorption spectroscopy analysis shows that these localized excitons transfer to normal [PbX 6 ] octahedra and become free excitons, which are further upconverted into free carriers at the band edge through electron−phonon interaction. As a result, anti-Stokes photoluminescence CsPb(BrI) 3 nanocrystals in glass is significantly enhanced. These results show that the quality of CsPbX 3 nanocrystals in glasses can be modulated by controlling the cooling process and regulate their optoelectronic properties.