Core-sheath fibers with the core component being a luminescent nanocomposite and the sheath component being poly(vinyl pyrrolidone) were prepared via the method of co-axial electrospinning; the luminescent nanocomposite consisted of a silicone rubber matrix with the complex Eu(TTA)(3)phen (TTA: 2-thenoyltrifluoroacetone, phen: 1,10-phenanthroline) as the filler. The fluorescence spectra, fluorescence lifetimes, and Judd-Ofelt parameters of the prepared core-sheath fibers were investigated. The results indicated that the Eu(TTA)(3)phen complex was uniformly dispersed in the silicone rubber as molecular clusters and/or nanoparticles, leading to a high luminescence intensity and efficiency. Additionally, unlike the neat Eu(TTA)(3)phen complex and electrospun fibers of thermoplastic-based nanocomposites that had no appreciable difference in the fluorescence lifetime and luminescent quantum efficiency at 73 and 293 K, the prepared electrospun core-sheath fibers had a longer fluorescence lifetime and a higher luminescence quantum efficiency at 73 K due to the contribution of the silicone rubber matrix.