Abstract The influence of Cu content on the magnetic and magnetotransport properties of Fe 60Co 18Nb 6B 16− x Cu x ( x=0, 1) alloys has been studied by means of hysteresis loops, permeability and magnetoimpedance measurements. The formation of Cu clusters enhances the nucleation of the α-FeCo phase, refining the microstructure. This can explain the smaller coercivity values obtained for the Cu-containing alloy. Magnetic permeability and magnetoimpedance results are in agreement with coercivity data. Larger permeability and magnetoimpedance ratio are found in samples of Cu-containing alloys annealed at the beginning of nanocrystallization.