The aqueous solubilization of carbon nanotubes (CNTs) with the aid of a block copolymer possessing one polyelectrolyte block (namely polystyrene-b-sodium (sulfamate/carboxylate polyisoprene)) is reported. The solubilization protocol, based on the co-dissolution of the copolymer and the CNTs, leads to the formation of supramolecular assemblies on the side walls of the tubes. Electron microscopy as well as infrared spectroscopy and thermogravimetric analysis were employed as meaningful probes to identify the adsorption of the polymer onto the surface of CNTs and the composition of the final hybrid material. Viscosity measurements on solutions of the copolymer decorated CNTs indicate that the polyelectrolyte effect, which is observed in the case of net polymers, is preserved in a lesser extent in the case of the copolymer/CNTs dispersions.