We report a simple modification of poly(dimethylsiloxane) (PDMS) surfaces with poly(ethylene glycol) (PEG) through the adsorption of a graft copolymer, poly(l-lysine)-graft-poly(ethylene glycol) (PLL-g-PEG) from aqueous solution. In this approach, the PDMS surface was treated with oxygen plasma, followed by immersion into aqueous solution containing PLL-g-PEG copolymers. Due to the hydroxyl/carboxylic groups generated on the PDMS surface after oxygen plasma, the polycationic PLL backbone is attracted to the negatively charged surface and PEG side chains exhibit an extended structure. The PEG/aqueous interface generated in this way revealed a near-perfect resistance to nonspecific protein adsorption as monitored by means of optical waveguide lightmode spectroscopy (OWLS) and fluorescence microscopy.