Using density functional theory, the current investigation investigates the physical attributes of the halide double perovskites Li2AgAsZ6 (Z = F, Cl, Br, I). The cubic layout and values of the octahedral and tolerance factors have been evaluated to confirm phase stability. The formation energy of each perovskite has been calculated to ensure thermodynamic stability. The electronic properties have been elaborated, which indicates the semiconductor behavior of Li2AgAsZ6. The calculations exhibited that the energy band gaps of Li2AgAsF6, Li2AgAsCl6, Li2AgAsBr6, and Li2AgAsI6 are 2.35 eV, 2.08 eV, 1.57 eV, and 1.05 eV, respectively. We also computed and comprehensively studied the optical characteristics of these materials in the energy range of 0–8 eV. These materials demonstrate absorption bandwidth in the visible range and are viable contenders for optoelectronic applications. To determine the transport and thermodynamic aspects, we used the BoltzTraP and Gibbs2 codes, respectively. The figures of merit values are observed as 0.79, 0.77, 0.76, and 0.71, respectively. Thermodynamic properties confirm the high-temperature stability of studied materials. Finally, these perovskites can benefit photovoltaic and thermoelectric devices, further requiring experimental validation.