Cadmium sulfide (CdS) nanoparticles (NPs) with europium (Eu) and ytterbium (Yb) dopant concentrations in the range of 1% to 4% were efficiently obtained through a co-precipitation approach in the presence of air at room temperature. Structural, morphological and optical characteristics of CdS  :  Eu^3  + and CdS  :  Yb^3  + NPs were explored by x-ray diffraction, Fourier transform-Raman, ultraviolet-visible absorption spectroscopy, and photoluminescence studies. The realized CdS  :  Eu^3  + NPs (3%) demonstrate the best luminescence with three emission peaks at 470 nm (2.63 eV), 590 nm (2.1 eV), and 616 nm (2.01 eV) that correlates to the excitonic emission of CdS NPs.