This paper highlights the preparation and characterization of MgCo2O4 and Cr-doped MgCo 2O4 nanoparticles grown using a solid-state reaction route. The crystallinity and crystallographic phase structure have been investigated by the X-ray diffraction (XRD), which evidences the cubic crystal structure of MgCo2O4 with space group Fd3m. The crystallites of pristine MgCo2O4 have an average size of 18.88 nm, as determined by Scherrer’s formula. It exhibits an increment of crystallite size from 18.88 nm to 21.60 nm with Cr ions substitution in the MgCo2O4 matrix. Halder–Wagner (H–W) technique reveals the parallel results of crystallite size followed by the inversed behavior of dislocation density and lattice strain. The study of FESEM illustrates the aggregation of spherical nanostructures with well-dispersed grains. UV–Vis spectroscopy depicts an enhancement in absorption accompanied by blue shift and increase in Egfrom 4.22 eV to 4.85 eV after Cr addition. Dielectric measurements have revealed that the dielectric constant is noticed to reduce with the introduction of Cr into the MgCo2O4 crystal framework. The electrical resistivity reduces after Cr impurity is incorporated into MgCo2O4 and has been found to decrease with increasing temperature. Impedance analysis has been carried out on MgCo2O4 and Cr-doped MgCo2O4, and it is observed that Cr doping improves the impedance.