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Site-specific conjugation to cysteines of proteins often uses ester groups to link maleimide or alkene groups to polymers. However, the ester group is susceptible to hydrolysis, potentially losing the benefits gained through bioconjugation. Here, we present a simple conjugation strategy that utilizes the amide bond stability of traditional 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide/N-hydroxysuccinimide coupling while introducing site specificity. Hydrolytically stable maleimide-end-functionalized polymers for site-specific conjugation to free cysteines of proteins were synthesized using reversible addition–fragmentation chain-transfer (RAFT) polymerization. The alpha terminus of the polymers was amidated with a furan-protected aminoethyl maleimide using carbodiimide-based chemistry. Finally, the maleimide was exposed by a retro Diels–Alder reaction to yield the maleimide group, allowing for thiol-maleimide …