This article present an reports on optical and band gap study of rare earth doped (RE = Tb3+, Pr3+, Ce3+, Dy3+ and Ce3+/Pr3+ ions) KSr(PO4) nanoparticles. The KSr(PO4) phosphor is synthesized by wet chemical method at 120 °C in a hot oven. Pure phase of KSr(PO4) phosphor material is achieved by sintering it at 950 °C for 2 h in muffle furnace. Photoluminescence investigation shows that KSr(PO4) doped with Tb3+, Pr3+ ions shows an emission in visible to NIR range after exciting it under UV and visible wavelength. Whereas, KSr(PO4) doped with Ce3+/Pr3+ ions shows the emission in NIR range extend from 650 to 800 nm, under 295 nm excitation band. Further Dy3+ doped ions, shows the characteristics emission band that corresponds to blue and yellow region, under UV excitation. The observed emission bands of Ce3+, Tb3+, Pr3+ and Dy3+ ions are assigned due to d–f and f–f transition respectively. Also the band gap of the prepared phosphor is found to be approximately 4.9 eV. Study on micro and nanocslae nature of phosphor are carried out by SEM, HRTEM analysis, indicating the core shell structure of materials with spherical shaped nano particles.