W-type Barium based ferrites with composition BaZn 2-x Ni x Fe 16 O 27 for (x ═ 0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by chemical co-precipitation technique by 8h sintering at 1100 0 C in order to investigate their structural and electrical properties. XRD patterns confirmed the formation of w type phase. It was observed that, initially the crystallite size increased from 15.285nm to 16.056nm with increasing concentration of nickel up to x = 0.1 but then gradually decreased to 15.68nm up to x = 0.4. This decrease showed that nickel act as crystallite inhibitor. Lattice constants decrease with increasing concentrations of substituted ions attributed to the fact that ionic radius of nickel (0.069nm) is less than that of zinc (0.072nm). X-ray density increased from 2.43 to 2.50g/cm 3 with increase in nickel concentration up to x = 0.3 and then decrease to 2.47g/cm 3 . As the atomic weight of nickel (58.69 amu) is smaller than zinc (65.37 amu). So the X-ray density should decrease with increasing nickel contents but here increase contradicted which may be due to variations in lattice distortions. FTIR spectra showed three frequency bands corresponding to tetrahedral, N-O stretching vibration of NO 3 ions, stretching and twisting of ־OH surface hydroxy group respectively. Resistivity increased with increase in nickel concentration from 0.59×10 7 Ω cm to 5.45×10 7 Ω cm.