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In this study, nanoparticles of Co1–xMnxCr2O4 (x = 0, 0.3) were synthesized by sol–gel method. The phase identification of the obtained samples was performed by X-Ray diffraction proving their crystallization in the cubic structure with the Fd3¯m\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Fd\bar{3}m$$\end{document} space group. The sample purity and morphology were studied by energy dispersive of photon X and scanning electron microscopy. Optical properties were investigated by Fourier transform infrared spectroscopy and Raman scattering analysis. The impedance spectroscopy technique over the temperature range from 420 to 660 K was used in order to understand the relaxation process and the evolution of the electrical behavior in these materials. Accordingly, the experimental data of the real and imaginary parts of the impedance were fitted to the equivalent circuit Rg//C//CPE. As a matter of fact, the activation energies extracted from the imaginary part of the electrical modulus, the imaginary part of the impedance, from the grain resistance Rg and the electrical conductivity were closed and affirm a transformation of the electrical behavior confirmed by a decrease of the material resistance after substitution of Co cations by Mn ones. The study of the AC conductivity shows a Jonscher’s behavior and a thermally activated conduction process, by CBH model, which become clearer after the substitution.