Rapid and scalable preparation of polymer-based magnetic microcapsules (MMCs) without employing any templates and surfactants is still a challenge. Herein, we present a one-step template/surfactant-free strategy for fast and large-scale fabrication of poly(vinyl alcohol) (PVA)-based MMCs. The MMCs are formed from simultaneous creation of magnetic Fe3O4 nanoparticles and crosslinking of PVA chains, which is achieved by simple addition of ammonia solution into the preformed water-in-oil (W/O) emulsion comprising castor oil, aqueous mixture of PVA and iron salts. The size and shell thickness of MMCs could be readily controlled by fine tuning the process parameters. Furthermore, this approach allows for incorporation of additional functional nanoparticles into the PVA shell of MMCs, as demonstrated by the fabrication of Pt nanoparticles decorated MMCs (Pt-MMCs) in this study. The Pt-MMCs displayed favorable catalytic activity for reduction of aromatic nitro compounds (e.g., 4-nitrophenol and 4-nitroaniline), and could be conveniently recycled using magnet and reused for > ten times without obvious decline of catalytic activity. This work thus opens a new pathway for facile fabrication of property-tailored MMCs to meet the requirements of various applications.