Optically transparent Er³⁺/Tm³⁺/Yb³⁺ tri-doped oxyfluoride tellurite based nano-crystallized glass ceramics with the batching composition of 73TeO₂-15ZnO-7ZnF₂-3YF₃-1.5YbF₃-0.3ErF₃-0.2TmF₃ (mol%) is prepared by a conventional melting quenching and the subsequent heat treatment processes. The sizes of grown nano-crystals in glass matrix appear to be smaller than 100 nm from the scanning electron microscope measurement. Visible up-conversion luminescence of the as melted glass and glass ceramics is investigated. The three-color up-conversion luminescence intensities by 980-nm pumping are increased significantly due to the heat treatment, and the blue intensity increases with a higher magnitude than other wavelengths after heat treatment.