We report a new type of highly efficient visible light-driven photocatalyst, Sm3+-activated BiOF nanoparticles, developed by a facile solid-state reaction technology. The corresponding phase compositions, morphological nature, and chemical states along with complementary theoretical calculation insights are investigated systematically. Upon 404 nm laser excitation, the photoluminescence performance of the synthesized nanoparticles is explored and the optimal properties are achieved in BiOF:xSm3+ (x = 0.07). The dipole-quadrupole interaction is attributed to the concentration quenching mechanism. Under visible light irradiation, the degradation of the RhB dye by utilizing the Sm3+-activated BiOF nanoparticles is studied. In comparison with the BiOF nanoparticles, the resultant compounds doped with Sm3+ ions demonstrate improved photocatalytic performance. Moreover, on the basis of density functional theory, the electronic structure of the BiOF impacted by Sm3+ ion doping is studied in detail by first-principles calculations, revealing the generation of an impurity energy level that is beneficial for enhancing the photocatalytic properties. Importantly, the h+ and •O2- active species play a deterministic role in promoting the degradation of the RhB dye. Compared to commercial ZnO nanoparticles, the developed nanoparticles exhibit superior photocatalytic activities, further elaborating that the Sm3+-activated BiOF nanoparticles are poised to be one of most promising visible light-driven photocatalyst candidates.