Influence of Mn partial substitution for Fe on the magnetic and magnetoimpedance properties of Fe73.5-xMnxSi13.5B9Nb3Cu1 (x = 1, 3, and 5) nanocomposite ribbons were investigated. The results indicated that the Mn addition led to an improved exchange coupling between grains and hence in the magnetic softness. Consequently, the giant magnetoimpedance (GMI) effect was significantly enhanced in these nanocomposites. In the frequency range of 0.1-10 Mhz, the GMI ratio reached the highest values of 83%, 94%, and 130% at the frequency of 2 MHz for x = 1, 3, and 5 compositions, respectively. The corresponding field sensitivity of GMI reached the highest values of 6, 7, and 16 %/Oe, respectively. These indicate that Fe73.5-xMnxSi13.5B9Nb3Cu1 (x = 1, 3, and 5) nanocomposites are potential candidate materials for making GMI sensors.