Studying the linear and non-linear optical properties is critical in terms of technological application, as it aids in developing the semiconducting materials for optoelectronic applications. Consequently, the present studies report the investigation of the influence of thermal annealing on the structural, morphology, linear, and non-linear optical properties of Ge₁₀Se₇₈Ag₁₂ thin films. X-ray diffraction analysis confirmed the amorphous state of Ge₁₀Se₇₈Ag₁₂ composition. The studied composition was annealed at a temperature between the glass transition and crystallization, and the annealing temperature T_an affected the number and intensity of crystalline phases. Some peaks disappeared at 383 K, indicating that this temperature represents a transition in the structure of the studied materials. The morphological changes caused by the thermal treatment were observed by the scanning electron microscopy (SEM). On the other hand, the linear and non-linear optical constants varied with T_an. The band gap was found to decrease from 1.70 to 1.43 eV and then increase to 1.91 eV with increasing the temperature from 363 to 573 K, confirming the presence of structural transition at 383 K. The optical and electrical conductivities were determined and found to vary with the temperature. The present results were analyzed and discussed.