In this study, we have investigated the electronic , structural, elastic, optical and thermodynamic properties of the copper-based ternary semiconductors, that is, KCuZ (Z= Te, Se). The properties of these materials have been precisely determined based on first-principle calculations. The lattice constants, bulk modulus and equilibrium total energies were obtained from Murnaghan equation of state and have a good agreement with other theoretical and experimental methods. The absorption spectra was analyzed to determine the active window of electromagnetic spectrum of the compounds. The elastic constants of these materials were elucidated and hence provided vital information about the material’s ability to withstand external stress. The results indicate that the materials conform to the stability criteria with brittle behavior and anisotropic nature in the HCP structure. The electronic band structures and density of states were computed and the results obtained suggests that the these materials have a band gap of 1.25 eV and 1.1 eV for KCuTe and KCuSe respectively and therefore they are suitable for photovoltaic applications. The materials are also found to posses desirable optical properties i.e. the materials have a good optical absorption since highest absorption peaks occur within the UV region, small reflectivity and high dielectric constant indicating that the materials is suitable for use as solar absorbers. •KCuTe and KCuSe are both hexagonal in nature and belong to space group P63/mmc.•KCuTe and KCuSe structures are mechanically and thermodynamically stable.•All the two compounds are brittle.•Band gaps of 1.1 eV for KCuSe and 1.25 eV fo KCuTe.