In this research, ab initio investigation on the electronic, magnetic, and structural properties of 3d transition-metal (TM) impurities (Cu, Ni, Co, Fe, Mn, Cr, and V) doped armchair (5, 5) indium phosphide nanotubes (InPNT) was performed by using a density functional theory. The observations illustrate that there exists a structural distortion around 3d TM impurities with regard to the pure InPNT. Furthermore, the observations revealed that the total magnetic moment changes are in good agreement with Hund’s rule. In addition, the Mn-doped InPNT has a maximum magnetic moment. The calculations exhibited that the InP nanotube is semiconductor in nature with a direct band gap of 1.46 eV. Also, the simulation results illustrated that when 3d TM impurities, except Cu, are replaced with In atom in InPNT, impurity doping leads to the magnetic form of the nanotube. Cu-doped InPNT is a non-magnetic metal whereas, Ni and Fe-doped InPNTs are ferromagnetic metals. The V-doped InPNT is also a magnetic semiconductor according to simulation data. Furthermore, we found that the Cr, Co, and Mn-doped InPNT are half-metals with 100% spin-polarization characters. This fact makes the InPNT used for Nano magnet and spintronic applications. In the end, our results show that the InP nanotube doped with iron is more stable than others.