AbstractIn this work, the authors report a novel single‐step, one‐pot process for the synthesis of self‐assembled nanoparticles using a polymerization‐induced self‐assembly (PISA) mechanism. In contrast to conventional approaches employing a pre‐formed macromolecular stabilizer, the disparate reactivities between two monomers, oligo(ethylene glycol) methyl ether methacrylate (OEGMA) and diacetone acrylamide (DAAm), are exploited instead to synthesize a gradient copolymer directly in aqueous solution. Due to the hydrophobicity of poly(DAAm), these gradient copolymers can self‐assemble in situ to form spheres and worms stabilized by the OEGMA residues. A surprisingly broad range of parameters are identified in which the worm morphology can be stabilized, which is highlighted by significant gelation of the reaction mixture in situ. This single‐step gradient copolymerization approach to PISA is more efficient than conventional two‐step syntheses. These results demonstrate improved reproducibility owing to the production of self‐assembled nanoparticles directly in a one‐pot and single‐step synthesis.