Soft interface materials have an immense potential for the improvement of biointerfaces, which are the interface of biological and artificially designed materials. Controlling the chemical and physical structures of the interfaces at the nanometer level plays an important role in understanding the mechanism of the functioning and its applications. Controlled radical polymerization (CRP) techniques, including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization, have been developed in the field of precision polymer chemistry. It allows the formation of well-defined surfaces such as densely packed polymer brushes and self-assembled nanostructures of block copolymers. More recently, a novel technique to prepare polymers containing biomolecules, called biohybrids, has also been developed, which is a consequence of the advancement of CRP so as to proceed in an aqueous media with oxygen. This review article summarizes recent advances in CRP for the design of biointerfaces.