As a rapid, controllable, and easily transferrable approach to the preparation of antimicrobial nanoparticle systems, a one-step, light-driven procedure was developed to produce asymmetric hybrid inorganic-organic nanoparticles (NPs) directly from a homogeneous Ag/polymer mixture. An amphiphilic triblock polymer was designed and synthesized to build biocompatible NPs, consisting of poly(ethylene oxide) (PEO), carboxylic acid-functionalized polyphosphoester (PPE), and poly(l-lactide) (PLLA). Unexpectedly, snowman-like asymmetric nanostructures were subsequently obtained by simply loading silver cations into the polymeric micelles together with purification via centrifugation. With an understanding of the chemistry of the asymmetric NP formation, a controllable preparation strategy was developed by applying UV irradiation. A morphology transition was observed by transmission electron microscopy over the UV irradiation time, from small silver NPs distributed inside the micelles into snowman-like asymmetric NPs, which hold promise for potential antimicrobial applications with their unique two-stage silver release profiles.