Polymerisation-induced self-assembly (PISA) is a modern methodology to synthesise well-defined nanostructures under concentrated reagents conditions in a reproducible way. Atom transfer radical polymerisation (ATRP) is a controlled radical polymerization that has rarely been employed in PISA. Moreover, because of the transition-metal catalyst traditionally employed in ATRP, it suffers from evident drawback for applications in biocompatible environments or in the presence of living material. However, it has recently been demonstrated that ATRP could be catalysed by metalloproteins (bioATRP) such as laccase, horse radish peroxidase or haemoglobin. Herein, we present the atom transfer radical polymerisation-induced self-assembly (ATR-PISA) of diblock copolymers into nanostructures catalysed by the metalloprotein myoglobin under mild aqueous conditions. This opens the road for the easy synthesis of nanostructures for biomaterials, living matter encapsulation or in situ formation of nano-objects.