A series of samples of the system NiGd x Fe 2 - x O 4 (x=0,0.1,0.3,0.5 and 0.7) were prepared by the usual ceramic technique. X-ray diffraction, infrared spectroscopy (IR) and electron spin resonance (ESR) have been used to study the mixed ferrite NiGd x Fe 2 - x O 4 . The X-ray analysis establishes that the samples x=0 and 0.1 have spinel phase structure but x=0.3 and 0.5 samples posses second phase (orthorhombic) besides the spinel one. The main two bands were observed by IR spectra recorded in the range 200-1000cm - 1 . The bands at 579cm - 1 (ν 1 ) and 397cm - 1 (ν 2 ) were assigned to tetrahedral (A site) and octahedral (B site) group complexes, respectively. The presence of the bands ν 1 and ν 1 1 around ν 2 at 307 and 455cm - 1 is the evidence of the entry of Gd 3 + ions instead of Fe 3 + ions at B site; and these bands appear due to (Gd 3 + -O 2 - ) stretching vibration. The line width of the ESR spectra decreases with the increased addition of Gd 3 + and the ferrite begins to have low electric loss which is very important in application as a core of transformer in microwave region. The DC conductivity was found to increase with increasing temperature. Curie temperature T c decreases as the nonmagnetic Gd ions increase. NiGd ferrite shows p-type conductivity due to the presence of Ni 2 + and Ni 3 + . The addition of Gd 3 + ions creates second orthorhombic phase at x>=0.3 besides the spinel one. The second intergranual insulating phase increases the resistivity of the samples. The activation energy of conductivity E σ and that for mobility E μ show a good agreement which gives evidence for the presence of hopping conduction in the ferrimagnetic region.