The pink persistent phosphor La₃GaGe₅O₁₆:Pr³⁺ was prepared successfully via a traditional solid state reaction method. In this paper, the La₃GaGe₅O₁₆ host is proved to be a new self-activated luminescent host lattice on the basis of excitation and emission spectra. The La₃GaGe₅O₁₆ host gives a blue emission under excitation at 260 nm. In the emission spectrum for La_2.99GaGe₅O₁₆:0.01Pr³⁺, two dominant peaks arise from a ³P₀ → ³H₄ transition in the blue region and a ¹D₂ → ³H₄ transition in the red region, respectively. However, concentration quenching of Pr³⁺ in La₃GaGe₅O₁₆:Pr³⁺ occurs at a low Pr³⁺ content of 0.02 in this work, which is mainly due to a dipole–dipole interaction. La₃GaGe₅O₁₆:Pr³⁺ phosphors exhibit pink persistent luminescence after short UV-irradiation. The optimal concentration of Pr³⁺ for the long persistent luminescence in the La₃GaGe₅O₁₆ host is experimentally about 0.01. The long persistent luminescence of La₃GaGe₅O₁₆:Pr³⁺ is discussed in accordance with the afterglow decay and thermoluminescence analysis. A model is proposed based on the experimental results to explain the mechanisms of the photoluminescence and afterglow phenomenon.