The effect of V doping on the structure and optical properties of LiMgPO4 was studied. We found that LiMg(PO4)1−x(VO4)x with x<17% V retains the crystal structure of LiMgPO4 and demonstrates self-activated luminescence. All emission spectra under 320 nm excitation had the form of a broad band with a maximum at 490 nm and the emission intensity increased with the vanadium concentration. The luminescence with a peak at 560 nm was also observed for LiMgVO4. The UV–Vis diffuse reflectance spectra were recorded for LiMgPO4, and LiMgPO4 with 17% V and LiMgVO4, and the optical band gaps were estimated to be 4.05, 3.90 and 3.43 eV, respectively. The ab initio calculations predict an absorption-edge shift to lower energies with growing vanadium concentration and reproduce very well the experimental band gaps for vanadium containing oxides (LiMgP0.75V0.25O4 and LiMgVO4), but provide a much larger value for LiMgPO4.