Novel and functionalized multiwalled carbon nanotubes (MWCNTs) were successfully synthesized using zwitterionic structure, consisting of quaternary amine and sulfonic acid groups. The zwitterionic MWCNTs were introduced into a polyethersulfone (PES) matrix to prepare ultrafiltration membranes, via the phase inversion method. The acid-functionalized MWCNTs were then mixed with the membrane matrix as reference. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy validated the introduction of quaternary amine and sulfonic acid groups into the MWCNTs. For example, the hydrophilicity of the composite membranes, especially of zwitterionic MWCNTs/PES composite membranes, was obviously improved, as compared with that of the pristine PES membrane. Also, the morphologies of the membranes were studied by field emission scanning electron microscopy (FESEM) and their permeability and antifouling properties were thoroughly investigated. The results show that the water flux of the composite membrane, containing 0.2 wt% of zwitterionic MWCNTs, was twice more than that of the pure PES membrane, and its flux recovery ratio was as high as 85%.