Photoinduced processes have been widely utilized in macromolecular synthesis through radical, cationic, anionic, and controlled/living polymerizations and ligation processes. 'While widely utilized, their application in step-growth polymerization has been scarcely investigated. In the present work, we report a new facile photochemical approach for the synthesis of polypyrene (PPy) by step-growth polymerization. Inspired by our previous studies on photoinduced electron-transfer reactions occurring between electron-rich monomers such as thiophene and carbazole derivatives and iodonium salt, we show that pyrene (Py) readily polymerizes under 350 nm irradiation at room temperature in the presence of iodonium salt by consecutive excitation, electron transfer within the exciplex, proton release, and coupling reactions. A detailed investigation on the structural, morphological, electrochemical, and molecular weight characteristics of the polymers revealed that the ratio of iodonium salt/Py plays a crucial role in the chain length and properties. The approach developed here is broadly adaptable to functional pyrenes and other conjugated monomers.