Synthesized nano-ferrits of Cobalt-Erbium having chemical formula CoErxFe2−xO4(x = 0 to 0.030 with step size 0.05) were characterized using X-Ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Structural variables that include lattice constant (a), crystallite size (D), X-ray density (dx) and surface area (s) were computed from XRD patterns. XRD patterns confirmed single phase cubic spinal structure while TEM results revealed homogeneous nature of particles accompanied by clusters without impurity peaks. The observed results are explained on the basis of composition.