In this work, nonfouling zwitterionic polymers were grafted via surface-initiated atom transfer radical polymerization (ATRP) from surfaces covered with an adhesive catechol initiator. The catechol initiator was attached to both bare gold and amino-functionalized surfaces, and the nonfouling performances of the resulting polymer brushes were compared. Under optimal conditions, ultralow protein adsorption from both single-protein solutions of fibrinogen and lysozyme and complex media of 10% blood serum and 100% blood plasma/serum was achieved. Furthermore, the 3-day accumulation of Pseudomonas aeruginosa on the treated glass surfaces was studied in situ using a laminar flow chamber. The results showed that these zwitterionic coatings dramatically reduced the biofilm formation of P. aeruginosa as compared to the reference bare glass.