A one-step core/shell electrospinning technique was exploited to fabricate uniform luminous perovskite-based nanofibers, wherein the perovskite and the polymer were respectively employed in the core and the outer shell. Such coaxial electrospinning technique enables the in-situ formation of perovskite nanocrystals, exempting the needs of pre-synthesis of perovskite quantum dots or post-treatments. It was demonstrated that not only the luminous electrospun nanofibers could possess color-tunability by simply tuning the perovskite composition, but also the grain size of the formed perovskite nanocrystals was largely affected by the perovskite precursor stoichiometry and the polymer solution concentration. Consequently, the optimized perovskite electrospun nanofiber yielded a high PLQY of 30.9%, significantly surpassing the value of its thin-film counterpart. Moreover, owing to the hydrophobic characteristic of shell polymer, the prepared perovskite nanofiber was endowed with a high resistance to air and water. Its PL intensity remained constant while stored under ambient environment with a relative humidity of 85% over a month and retained intensity higher than 50% of its initial intensity while immersed in water for 48 h. More intriguingly, a white light-emitting perovskite-based nanofiber was successfully fabricated for the first time by pairing the orange light-emitting compositional perovskite with a blue light-emitting conjugated polymer.