Optical fber with YPO4:Pr3+ nanocrystals (NCs) is presented for the frst time using the glass powder— NCs doping method. The method’s advantage is separate preparation of NCs and glass to preserve luminescent and optical properties of NCs once they are incorporated into optical fber. The YPO4:Pr3+ nanocrystals were synthesized by the co-precipitation and hydrothermal methods, optimized for size (< 100 nm), shape, Pr3+ ions concentration (0.2 mol%), and emission lifetime. The core glass was selected from the non-silica P2O5-containing system with refractive index (n= 1.788) close to the NCs (no = 1.657, ne= 1.838). Optical fber was drawn by modifed powder-in-tube method after pre-sintering of glass powder—YPO4:Pr3+ (wt 3%) mixture to form optical fber preform. Luminescent properties of YPO4:Pr3+ and optical fber showed their excellent agreement, including sharp Pr3+ emission at 600 nm (1 D2–3 H4) and 1 D2 level lifetime (τ = 156 ± 5 µs) under 488 nm excitation. The distribution of the YPO4:Pr3+ NCs in optical fber were analyzed by TEM-EDS in the core region (FIB-SEM-prepared). The successful usage of glass powder—NCs doping method was discussed in the aspect of promising properties of the frst YPO4:Pr3+ doped optical fber as a new way to develop active materials for lasing applications, among others.