Structural, photoluminescence, dielectric, and ferroelectric properties of lead-free perovskite Pr3+-doped xK0.5Bi0.5TiO3–(1−x)Na0.5Bi0.5TiO3 (x = 0–1.0) thin films were studied. The thin films were prepared by a chemical solution deposition method combined with a rapid thermal annealing process at 700°C. We observed that the thin film with x = 0.15, corresponding to the morphotropic phase boundary in the solid solution ceramics or single crystal bulk counterparts, showed a very large dielectric constant and a high remanent polarization, as well as a strong red emission at 611 nm assigned to 1D2[RIGHTWARDS ARROW]3H4 transitions of the Pr3+ ions. In addition, this study also indicates that the morphotropic phase boundary in xK0.5Bi0.5TiO3–(1−x)Na0.5Bi0.5TiO3 thin films might be probed by photoluminescence probe of Pr3+ ions because the photoluminescence of Pr3+ ions is very sensitive to the phase structure changes.