The authors prepared a near-UV to red wavelength conversion thick film containing 38.8 wt% of YVO4:Bi3+,Eu3+ nanoparticles of 10.8 ± 1.6 nm in size. This nanoparticle film shows a high transparency in the visible region, e.g., the transmittance at 619 nm is ∼ 96% irrespective of the film thickness. The photoluminescence intensity at 619 nm corresponding to the f-f transition of Eu3+ for this nanoparticle film increases with increasing the film thickness up to 400 μm, whereas that of the film containing micron-sized particles reaches the maximum at the film thickness of ∼ 40 μm. On the other hand, YVO 4:Bi3+,Eu3+ nanoparticles have a sufficient photostability for practical use over 15 years outside, as confirmed by the light fastness test. These results suggest that the transparent film of YVO 4:Bi3+,Eu3+ nanoparticles are potentially applicable to the spectral convertor for photovoltaic cells from the aspects of low light-scattering loss and high photostability.