A series of star-shaped block (SBC) and random (SRC) copolymers containing poly(ethylene glycol) methyl ether methacrylate (PEGMA) and methyl methacrylate (MMA) moieties were prepared by atom transfer radical polymerization (ATRP), and used as membrane coating materials to investigate the effects of polymer structure and monomer content on the antifouling properties of the membranes. Polysulfone (PSf) ultrafiltration membranes coated with SBCs showed noticeably higher bio- and oil-fouling resistance than the bare PSf membrane. In addition, the SBC-coated membranes exhibited better antifouling properties than the SRC-coated membrane during both BSA solution and oil/water emulsion filtrations. The enhanced antifouling properties of the SBC-coated membrane compared to the SRC-coated one were ascribed to the larger content of denser PEG segments on the membrane surface, resulting in decreased interactions with proteins and oils.