The citric-nitrate technique was used to synthesize polycrystalline Nd2Ni1-xCoxMnO6−δ (0.2 ≤ x ≤ 0.5) perovskite oxide. Phase formation was studied by X-ray powder diffraction (XRPD). The unit cell parameters and unit cell volume were refined by the Rietveld analysis, increase with the increasing doping concentration of cobalt. The optical study was performed for the samples in the range of 200–800 nm using UV–vis spectroscopy an absorption peak has been observed in around 330 nm. The energy bandgap (Eg) of the studied samples is slightly influenced by the increasing concentration of cobalt due to the interaction of electronic states between doped Co and other 3d metals. Partial substitution of nickel by cobalt at B-site decreases the Curie temperature (TC) and increased the irreversibility between the zero-field cooled (ZFC) and field-cooled (FC) below TC. The decreasing tendency of TC for the studied samples with the increasing concentration of cobalt in Nd2Ni1-xCoxMnO6−δ might be associated with the decreasing Ni/Co–O–Mn bond angle.