A highly efficient room-temperature synthetic route to bioconjugable polymeric nanoparticles in the 5-20 nm size range based on single-chain intramolecular click cycloaddition is described. It is illustrated by preparing single-chain cross-linked polymeric NPs from poly[MMA-co-(3-azidopropyl methacrylate)-co-(3-trimethylsilyl-propyn-1-yl methacrylate)] terpolymers using a one-pot procedure and a continuous addition technique. For polymeric NPs with an excess of azide groups, aminoacid/PMMA NPs were easily obtained by performing a second click reaction with propargyl glycine. This versatile and general method opens the way to the synthesis of other kinds of polymeric and bioconjugated NPs beyond those reported in this communication.