Unwanted nonspecific adsorption caused by biomolecules influences the lifetime of biomedical devices and the sensing performance of biosensors. Previously, we have designed B-M-E triblock proteins that rapidly assemble on inorganic surfaces (gold and silica) and render those surfaces antifouling. The B-M-E triblock proteins have a surface-binding domain B, a multimerization domain M and an antifouling domain E. Many biomedical technologies involve organic (polymeric) surfaces where B-M-E triblock proteins could potentially be used. In this study, we computationally and experimentally investigate the assembly of B-M-E triblock proteins on polystyrene (PS) surfaces, using PS-binding peptides as a surface-binding block B. We used atomic force microscopy, dynamic light scattering, fluorescence microscopy and quartz crystal microbalance to test the antifouling coating functionality. We found that, like for inorganic surfaces, the B-M-E proteins with PS-binding peptides as B block, form homogeneous monomolecular layers on PS surfaces with good stability against PBS washing. The adsorbed protein layer fully prevents adsorption of fluorescently labeled bovine serum albumin to PS microfluidic chips. Similarly, no significant fouling was observed using quartz crystal microbalance when 1 % (v/v) or 10 % (v/v) human serum were used as foulants.