The doping of the spinel ferrites with selective cations usually improves the properties of the parent ferrite. The effect of Co2+/Gd3+ co-substitution on the microstructure, optical, and magnetic properties of Cu1–xCoxFe2–xGdxO4 prepared by the citrate-nitrate auto-combustion synthesis was investigated. Characterization of the samples was performed with powder X-ray diffraction (XRD), Raman and Fourier-transform infrared (FTIR) spectroscopy, field-emission scanning electron microscopy, X-ray energy-dispersive spectroscopy, UV-Vis spectroscopy, and a vibrating sample magnetometer. The results of XRD, Raman, and FTIR analysis show a gradual structural phase transition from a tetragonal (I41/amd) structure to a cubic (Fd3¯m) structure. The bandgap energy of the studied samples is in a range of 1.57–1.75 eV with a minimum in sample x = 0.06 and then increases. Magnetic investigations show that the presence of Co2+/Gd3+ cations in an octahedral site of the copper ferrite structure could increase saturation magnetization and coercive field from 567.9 Oe and 23.62 emu/g to 929.4 Oe and 28.27 emu/g, respectively.