The cell adhesion was investigated oil polymer brushes of poly(2-hydroxyethyl methacrylate) (PHEMA), poly(2-hydroxyethyl acrylate) (PHEA), and poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) with different graft densities (in semidilute and concentrated regimes) and thicknesses. The concentrated polymer brushes (CPBs) of all the three, regardless of differences in chemical structure and hydrophilicity, almost completely Suppressed the adhesion of L929 fibroblast cell in contrast to the corresponding semidilute polymer brushes (SDPBs). Along with our previous study on excellent protein repellency of CPB owing to its unique size-exclusion effect (of entropic origin), we Concluded that such bioinertness Should be commonly found in CPB of neutral and hydrophilic polymers.