Gallium oxide (α−Ga2O3) is a new material of ultrawide bandgap semiconductor due to its high thermal stability and applicability in highly powered and ultraviolet optoelectronic devices. In spite of these benefits, it has poor optical response in the wavelengths above the ultraviolet region which restricts its use. Here, the impact of simultaneous calcium and magnesium co-doping into α−Ga2O3 crystal is investigated through firstprinciples calculations on the density functional theory on the generalized gradient approximation. The proposed Ca−Mg codoping strategy results in an increased bandgap and enhanced ultraviolet optical response without introducing detrimental defect states. The co-doping causes observable modifications of the electronic structure, which creates an increased bandgap and impurity-related states near the valence band maximum. The changes contribute to the movement of the optical absorption edge to lower photon energies and thus enhance the light absorption behavior. The analysis of the band structure, density of states, dielectric response, and absorption spectra show that it has increased optical activities and better dielectric performances than the pristine material. Calculations of the formation energy also verify the energy stability of the Ca−Mg co-doped system. The findings indicate that Ca−Mg co-doping presents a viable direction in adjusting the optical properties of α−Ga2O3 and therefore it is a material of interest to next-generation optoelectronics like photodetectors and solar-related applications. To the best of the authors knowledge, such a Ca−Mg co-doping approach for optical enhancement of α−Ga2O3 has not been previously reported.