We have studied the Ni_0.5Zn_0.5Fe₂O₄ nanoparticles, prepared by coprecipitation method and then annealed at three different temperatures (200, 500 and 800 °C), by employing X-ray diffraction (XRD) and Mössbauer spectroscopy techniques at room temperature. The average particle size is found to be ˜11.2 nm for 200 °C heat treated sample. The nano particles heat-treated at 200 °C show only a paramagnetic doublet whereas the sample heat-treated at 500 °C temperature shows a superparamagnetic doublet, and two collapse magnetic sextets (Zeeman splitting) with broad line widths. The sample, heat-treated at 800 °C, shows only two sextets. Mössbauer spectra reveal that the samples heattreated above 500 °C have a ferimagnetic phase. The values of isomer shift ([δ]) are consistent with Fe ions in trivalent state. The values of the quadrupole splitting for both sites (tetrahedral and octahedral) are close to zero, identifying a local cubic symmetry around Fe ions. The values of magnetic hyperfine fields (H_hf) vary with the changing annealing temperature; from 38.6 to 42.3 T for Fe_A (tetrahedral) and from 27.0 to 36.9 T for Fe_B (octahedral) when annealing temperature is varied from 500 to 800 °C.