Transparent zinc-tellurite glasses co-doped with Terbium ion (Tb³⁺) and Ytterbium ion (Yb³⁺) were successfully created using the melt-quench method in an air environment. Systematic investigations were conducted using X-ray diffraction, differential scanning calorimeter, UV-Visible-IR, and upconversion spectra to examine the structural, thermal, and optical properties. The absorption peaks from the Tb³⁺ transitions are located at 486 nm (⁷F₆ / ⁵D₄ ) in the Tb³⁺ single doped glass. The overlapping absorption bands are believed to be the result of the transition from ⁵D₀ to ³H₇ excited-state levels were observed. Under 978 nm laser stimulation, a zinc tellurite glass sample containing Tb³⁺ and Yb³⁺ ions showed strong, typical Tb³⁺ emissions (⁵D₄ - ⁷F_3-6 and ⁵D₃ - ⁷F_4-6). The upconversion’s laser power dependence demonstrated that the two-photon process was in charge of the green emission.