The synthesis of a new -cyclodextrin-hyperbranched polyethyleneimine (-CD-HPEI)/polysulfone (PSf) membranes via interfacial polymerization of trimesoyl chloride and -CD-HPEI is described in this paper. The membranes were characterized by atomic force microscopy (AFM), high resolution scanning electron microscopy (HR-SEM) and contact-angle measurements. Water permeability and rejection data were obtained using a cross-flow filtration system at 0.69MPa. The membranes were hydrophilic (25 degrees to 63 degrees), showed high humic acid rejection (>80%), and maintained a constant flux throughout the filtration. The modified membranes were rougher than the pristine PSf membranes but they exhibited better antifouling properties due to the hydrophilic surface which acted as a barrier against humic acid deposition. The modification of PSf with -CD-HPEI resulted in enhanced hydrophilicity and water permeability while still maintaining high humic acid rejection. Supplemental materials are available for this article. Go to the publisher's online edition of Separation Science & Technology to view the supplemental file.