(1 − x)ZnMn2O4/xNiFe2O4 (x = 0, 0.05, 0.1, 0.15, 0.2) nanocomposite samples were prepared employing co-precipitation procedure. Phase analysis of the measured x-ray diffraction patterns manifested the formation nanocomposites of two phases ZnMn2O4 (ZMO) and NiFe2O4 (NFO), and the phase percentage of each was determined applying Rietveld method. Analysis established the exchange of cations Zn, Mn, Ni, and Fe among the (ZMO) and (NFO) phases. Also, the influence of alloying parameter (x) on the cell parameters of (ZMO) and (NFO), crystallite size, and different IR vibrational bands was studied. For the prepared (1 − x)ZMO/xNFO nanocomposite samples, the influence of NFO amount of the absorbance, extinction coefficient, refractive index, optical bandgap, and other optical parameters were examined over different wavelength ranges using UV diffused absorption technique. The nonlinear optical behavior of the nanocomposite samples was increased as the percentage of NFO increases. The variations in the photoluminescence intensity and different emitted colors for the prepared nanocomposite samples were explored in detail.