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Photoluminescence (PL) properties of YPO4:Mn2+ and Zr4+-doped YPO4:Mn2+ have been investigated by measuring PL and PL excitation (PLE) spectra and electron spin resonance (ESR) spectra. The PL spectrum at 9 K is dominated by a red (R) emission band at 1.91 eV for YPO4:Mn2+ and a blue-green (BG) emission band at 2.52 eV for YPO4:Zr4+,Mn2+. The R and BG bands are caused by the d–d transition in Mn2+ ions, in analogy with PL spectra of Mn2+-doped inorganic compounds. The PLE spectra for the R and BG bands are different from each other, suggesting that the Zr4+ addition changes the environment of Mn2+ ions. The ESR spectra revealed that Mn2+ ions can occupy interstitial sites without Zr4+ addition and Y3+ lattice sites with Zr4+ addition. It is thus supposed that the R and BG bands originate in an interstitial Mn2+ ion and a Y3+-substituted Mn2+ ion, respectively. The increase in the BG emission intensity caused by Zr4+ addition can be explained as an increase in the number of Mn2+ ions at Y3+ sites.