The paper discusses the origin of emission quenching and the formation of metal-to-metal charge-transfer states in yttrium orthovanadate-arsenates doped with Tb3+ ions. For that purpose, a series of highly crystalline yttrium orthovanadate-arsenate nanoparticles (type YVxAs1–xO4, where x = 2–65 mol %) doped with Tb3+ ions were prepared using the co-precipitation method. The structural and morphological properties of the particles were studied by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) techniques. The photoluminescence spectral and dynamical properties of YVxAs1–xO4 doped with 1 mol % Tb3+ ions were investigated in detail. It was found that the emission quenching is related to changes in the band gap and Tb3+-to-V5+ metal-to-metal charge transfer. Further, the Tb3+-to-As5+ metal-to-metal charge transfer was identified and rationalized based on different models.