The strategy of this work is mainly concentrated on tuning the performance of CdO nanoparticles (NPs) via Tb2O3 addition. Precipitation method is utilized for the NPs synthesis, where Tb2O3 concentrations were 0%, 5%, 10% and 15%. The prepared samples are examined using different analytical techniques. SEM and TEM results showed that Tb2O3 acted as passivation agent for the growth of CdO NPs and annulled particles agglomeration. There is a harmony in crystallites size calculated from XRD and TEM (47–55 nm), whereas, the maximum value is obtained for 5% of Tb2O3. The molecular analysis using FTIR elucidated the stability of the absorption bands for the mixed phase samples comparing with the single one, in agreement with XRD results. The estimated Eg values are ranged within (2.90–2.94) ± 0.02 and are increased slightly with Tb2O3 content. The photoluminescence (PL) spectra using different excitation wavelengths showed two overlapped emission peaks for the mixed phase Tb2O3 - CdO NPs, where the positions and the shape of these peaks appeared to be independent on excitation wavelength. The maximum PL intensity is recorded for the 5% of Tb2O3 using an excitation wavelength of 365 nm. The high intensive of visible emission using different excitation wavelengths suggested the possibility of their use in diverse applications such as light emitting diodes, optical sensor as well as in cathode ray tubes.