A polymer based nanocomposite (NC) material embedded with highly luminescent nanopowders could be promising for replacing traditional luminescent materials from a technological pointof view.In this study, we have successfully obtained YPO4: Sm3+ /Polymer nanocomposite phosphor films by embedding YPO4: Sm3+ luminescent nanoparticles (NPs) for orange-light emitting diode (LED) applications. These luminescent NPs were synthesized using the sol gel method in different polymer matrices i.e. polystyrene (PS) and poly (methyl methacrylate) (PMMA) by using direct solution mixing. The structural, morphological, and photoluminescence characteristics of the nano-phosphors and resulting NC films were examined and discussed. The emission spectra of YPO4: Sm3+ (x at.%) nano-phosphors under near-UV excitation at 404nm were dominated by orange emission attributed to 6H5/2 4F7/2 (601nm) luminescence of Sm3+ ions. The optimum doping concentration of activator Sm3+ in YPO4 matrix was found to be 5 at.%. When the doping concentration of Sm3+ was higher than 5 at.%, concentration quenching occurred. The incorporation of YPO4: Sm3+ NPs into polymer matrices indicated that the NCs retained the original luminescence properties of the luminescent NPs, although a decrease in their emission intensity was observed for the NC films, attributable to a polymer matrix effect, which dominated in PS matrix. The fluorescence decay times of NPs in the NC films were measured and compared to those of proper YPO4: Sm3+ nano-phosphors. A decrease in decay time in NC film was observed due the effective refractive index effect. Temperature-dependent photoluminescence (TDPL) of PMMA NC film was studied in 100-400K range, investigating the thermal stability of the film. Additionally, CIE coordinates confirmed the red-orange light emission of the prepared phosphors and NC films. The obtained results indicate that the synthesized polymer-nanophosphor NC films are promising candidates for orange-LED applications.