Current research is a computational study in which we focus on calculating optical properties of Eu-doped Cadmium Sulfide (CdS) system. We employ Perdew–Burke–Ernzerhof (PBE)–generalized gradient approximation (GGA) for accomplishment of our study and we assume various Eu concentrations (3.12%, 6.25% and 9.37%) for doping into host CdS lattice. We substitute Cd atoms with Eu atoms while supercell size is kept fixed ([Formula: see text]. We present a detailed comparison among optical properties of pure CdS and various Eu concentrations. Partial density of states (PDOS) plots reveal hybridization among Cd [Formula: see text]-states, S [Formula: see text]-states and Eu [Formula: see text]-states and because of it, material (CdS:Eu) shows exceptional energy transfer which influences optical spectra and electronic properties. A considerable change in absorption spectra is noted, where in comparison to pure CdS, absorption shows blueshift with increasing Eu concentrations. Our DFT results were found to have great resemblance with existing literature. Addition of Eu into the CdS lattice originates novelty in CdS:Eu system and number of potential applications related to the field of biomedical physics, amperometric biosensors, quantum dots (QDs) sensors, photonics, bioprinting, biosensing luminophores, solar cells and optoelectronics industry may be explored in technological perspectives.