Rare-earth ion (Eu³⁺, Tb³⁺, Ce³⁺)-doped LaPO₄ nanocrystalline thin films and their patterning were fabricated by a Pechini sol–gel process combined with soft lithography on silicon and silica glass substrates. X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), atomic force microscopy (AFM), scanning electron microcopy (SEM), optical microscopy, absorption and photoluminescence (PL) spectra as well as lifetimes were used to characterize the resulting films. The results of XRD indicate that the films begin to crystallize at 700 °C and the crystallinity increases with increasing annealing temperature. The morphology of the thin film depends on the annealing temperature and the number of coating layers. The 1000 °C annealed single layer film is transparent to the naked eye, uniform and crack-free with a thickness of about 200 nm and an average grain size of 100 nm. Patterned thin films with different strip widths (5–50 µm) were obtained by micromolding in capillaries (soft lithography). The doped rare earth ions show their characteristic emission in the nanocrystalline LaPO₄ films, i.e., Eu³⁺⁵D₀–⁷F_J (J = 1, 2, 3, 4), Tb³⁺⁵D_3,4–⁷F_J (J = 6, 5, 4, 3, 2) and Ce³⁺ 5d–4f transition emissions, respectively. Both the lifetimes and the PL intensities of Eu³⁺ and Tb³⁺ increase with increasing annealing temperature, and the optimum concentrations for them were determined to be 5 mol% and 16 mol% of La³⁺ in LaPO₄ thin films, respectively. An energy transfer phenomenon from Ce³⁺ to Tb³⁺ has been observed in LaPO₄ nanocrystalline thin films, and the energy transfer efficiency depends on the doping concentration of Tb³⁺ if the concentration of Ce³⁺ is fixed.