Because of their exceptional physical and thermal properties, cellulose nanocrystals (CNCs) are a highly promising bio‐based material for reinforcing fillers. Studies have revealed that some functional groups from CNCs can be used as a capping ligand to coordinate with metal nanoparticles or semiconductor quantum dots during the fabrication of novel complex materials. Therefore, through CNCs ligand encapsulation and electrospinning, perovskite‐NC‐embedded nanofibers with exceptional optical and thermal stability are demonstrated. The results indicate that, after continuous irradiation or heat cycling, the relative photoluminescence (PL) emission intensity of the CNCs‐capped perovskite‐NC‐embedded nanofibers is maintained at ≈90%. However, the relative PL emission intensity of both ligand‐free and long‐alkyl‐ligand‐doped perovskite‐NC‐embedded nanofibers decrease to almost 0%. These results are attributable to the formation of specific clusters of perovskite NCs along with the CNCs structure and thermal property improvement of polymers. CNCs‐doped luminous complex materials offer a promising avenue for stability‐demanding optoelectronic devices and other novel optical applications. Perovskite/ cellulose nanocrystals (CNCs) encapsulated nanofiber (CNCs@PeNFs) for the white light‐emitting diodes through the electrospinning process are fabricated. The CNCs@PeNFs can maintain 90% intensity after five annealing cycles (from 20 to 140 °C) and 60% intensity after 6 h irritation of UV light, which are attributed to the complexation reaction between CNCs ligand and perovskite, and the cluster morphology within nanofibers.