Ni-Zn ferrites have important applications in the field of soft magnetic materials due to their excellent magnetic properties, but their high bulk density hinders their widespread use. CNT/nickel-zinc ferrite (CNT/Ni0.5Zn0.5Fe2O4) nanocomposites was prepared by sol-gel method, and sintered at 1000 °C to be used as an electromagnetic wave absorber. The results showed that the morphology, impedance matching, density, electrical conductivity and absorption coefficient of CNT/Ni-Zn ferrite was controlled by the additional CNT content. The NZ3 sample containing 0.06 g of CNT showed high conductivity, and high absorption coefficient. The amount of 0.06 g of CNT was a critical amount for the CNT/Ni-Zn ferrite nanocomposites. Above this value, the increasing trend toward improved nanocomposite properties due to the agglomeration of CNTs was reversed. The absorption performance of the CNT/Ni-Zn ferrite nanocomposites are attributed to the incorporation of dielectric and magnetic loss mechanisms in which the magnetic portion is comparable to the dielectric portion. Possessing excellent magnetic and absorption properties, it has the potential to be an excellent electromagnetic wave absorbing material.