Luminescent and flexible composite films constituted of core–shell SiO2@YAG:Tb3+ nanoparticles embedded in poly-N-vinylpyrrolidone (PVP) were elaborated by coat-master technique. The 500 nm silica cores and the fluorescent shells of nanoparticles were prepared by the sol–gel process through respectively the Stöber method and an alkoxide route. Their structure and morphology after annealing at 1000 °C for 1 h were respectively characterized by XRD and SEM analyses, evidencing the formation of a well crystallized YAG shell onto the surface of silica nanoparticles. Homogeneous dispersion of SiO2@YAG:Tb3+ nanoparticles into the PVP matrix was confirmed by TEM observations. Photoluminescence study led on both nanoparticles and composite films pointed out an efficient green fluorescence resulting from the strong 5D4→7F5 Tb3+ transition around 545 nm. The elaboration process used is both tunable and applicable to a large variety of powders and polymers because it does not require any additive to form homogeneous and easily shapeable core–shell nanoparticles/polymer nanocomposites applicable in various optical devices.