CoCr (x) Fe2-x O-4 (0.0 aecurrency sign x aecurrency sign 1.0) nanoparticles were synthesized by a microwave combustion method and the effect of Cr3+ substitution on structural, morphological, and magnetic properties of CoFe2O4 was studied. The structural, morphological, and magnetic properties of the products were determined and characterized in detail by X-ray diffraction (XRD), high-resolution scanning electron microscopy (HR-SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FT-IR), and vibrating sample magnetometer (VSM). Cation distribution of calculations confirmed the B site (octahedral site) preference of substituted Cr3+ ions. X-ray analysis showed that all compositions crystallize with a cubic spinel-type structure. The lattice parameter decreased from 8.384 to 8.362 with increasing Cr content. The average crystallite size was found in the range of 30.6-45.4 nm. Magnetization measurements showed that saturation magnetization of products decreases with the increase of the Cr substitution (x).