Using the first-principles calculations based on the spin-polarized density functional theory (DFT), we investigated the structural, electronic and magnetic properties of Cu-doped single walled ZnO nanotubes (SWZnONTs). Our results show that for a unit cell with 40 Zn and 40 O atoms, substitution of a single Zn atom by a Cu leads from a semiconductor to a ferromagnetic (FM) half-metallic phase transition with 100% spin polarization. In this case the total magnetic moment of super cell is 1.0 μB. To investigate the effects of Cu-codpoed SWZnONTs two different configurations are considered, first we assumed the two Zn atoms replaced by two Cu atoms are close and second they are far from each other. When Cu atoms are at the nearest-neighboring positions, the antiferromagnetism (AFM) phase is stable, while increasing the distance between the two Cu atoms, the ferromagnetism stability increases. In the AFM phase the structures are nonmagnetic semiconductors, but in the FM phase all these systems are half-metallic systems with 100% spin polarization, so it can be used as magnetic nanostructure and future applications in permanent magnetism, magnetic recording, and spintronics.