All‐inorganic cesium lead halide perovskite nanocrystals (IPNCs) exhibit exceptional optical properties but the low chemical and structural stability has restricted their long‐term applications. According to previous studies, hybridization of IPNCs with other matrix materials provides an efficient method for improving their optical stability. Here, we develop a new strategy to synthesize a chemically and structurally stable CsPbBr3 perovskite material using polymer nanofiber as the protective layer. It is found that CsPbBr3 nanocrystals grow spontaneously inside the polymer nanofiber. Furthermore, the crystal structure and grain size remain substantially unchanged for two months due to the presence of the polymer layer, resulting in a decrease in luminescence quenching. We expect that the results obtained in this work could open new possibilities for the design and development of air‐stable CsPbBr3 by hybridization with polymer nanofibers.