Polymeric coatings that can undergo effective functionalization with ligands and (bio)molecules necessary for intended applications are widely employed to engineer functional interfaces. Herein, amine-reactive polymer brushes are fabricated using a succinimidyl group-activated carbonate monomer, and their facile post-polymerization functionalization is demonstrated through ligand-mediated protein immobilization and detection. Copolymer brushes containing varying amounts of the reactive monomer and an ethylene glycol-based methacrylate comonomer were obtained using surface-mediated reversible addition fragmentation chain transfer polymerization. Post-polymerization functionalization of the thus-obtained copolymer brushes with a fluorine-containing amine, namely, 4-(trifluoromethyl)benzylamine, demonstrated highly efficient functionalization at ambient temperature. To demonstrate possible applications, polymer brushes functionalized with a bioactive ligand, namely, biotin, were used to detect the target protein, streptavidin. The biotin-streptavidin interaction on brushes could also be employed to conjugate protein-coated quantum dots. Importantly, comparison of the attachment of 4-(trifluoromethyl)benzylamine on activated carbonate group-containing brushes with reaction of the same molecule on traditional active ester-based brushes demonstrated higher extent of conjugation to carbonate brushes. Finally, orthogonal functionalization of the copolymer brushes with an amino-functionalized molecule and a maleimide-containing fluorescent dye in spatial control using microcontact printing was demonstrated. One can envision that the facile fabrication and efficient functionalization of succinimidyl carbonate-based amine-reactive brushes afford an attractive platform for applications using functional interfaces for diagnostic purposes.