Co-based amorphous ribbon Fe5.85Co70.15Mo4B15Si5 (Metglas 2705X) was coated by Nickel complexes in order to increase the giant magneto-impedance response. Influence of inorganic nickel complex coating on giant-magneto impedance (GMI) effect was investigated under varied applied dc fields (–8 kA/m < H dc < 8 kA/m) at a frequency range of 0.1–3.5 MHz. The results showed that the GMI effect and operating frequency on Co-based amorphous ribbons, which were coated by Ni film, have significantly improved as compared to the uncoated samples. The variations on permeability, transverse anisotpy and flux penetration in the coated ribbons cause this improvement in the GMI effect.