Carbon nanotube enhanced thin-film nanocomposite membranes were prepared by incorporating carbon nanotubes (CNTs) into the active layers of membranes used for water treatment. For inclusion into these active layers, a grafting procedure for carbon nanotubes was set up to increase their hydrophobicity. Multiwalled carbon nanotubes (MWNTs) grafted by poly(methyl methacrylate) (PMMA) were synthesized via a microemulsion polymerization of methyl methacrylate (MMA) in the presence of acid-modified multiwalled carbon nanotubes (c-MWNTs). Subsequently, polyamide thin-film nanocomposite (TFN) membranes containing PMMA–MWNTs were prepared via interfacial polymerization. Morphology studies demonstrate that MWNTs have been successfully embedded into the active polyamide layer. The rejection of Na 2 SO 4 was high (99%), and the water flux was about 62% increased compared to the thin-film composite membrane when using 2g/L piperazine (PIP) in the aqueous phase, 4g/L trimesoyl chloride (TMC) and 0.67g/L PMMA–MWNTs in the organic phase, which demonstrates that PMMA–MWNTs significantly improve selectivity and permeability.