Nano-sized powders of rare-earth ions added CdFe_2O_4 ferrites were synthesized by oxalate co-precipitation method. The influence of R ions (R = Sm~(3+), Y~(3+), and La~(3+)) on the microstructure and magnetic properties of CdFe_2O_4 ferrites was studied. XRD, SEM, FTIR, and magnetic hysteresis loops were used for analyzing the samples. The addition of R ions alters the structure of the powders and decreases the crystalline size, lattice constant, and grain size. The magnetic properties such as saturation magnetization, remanent magnetization, and magnetic moment increased due to addition of rare-earth ions in CdFe_2O_4 ferrite. The formation of secondary phase on the grain boundaries supports the abnormal growth. FTIR spectra show two absorption bands. Results suggest that the magnetic properties depend on the particular method of preparation and additives.