Silver halide-based structures have been attracting great interest as efficient visible-light-driven photocatalysts towards the photodegradation of organic pollutants, and those studies focusing on their morphology-dependent catalytic performances have received particular attention. While great advancements in this regard have been witnessed in the past few years with respect to AgCl- and AgBr-based photocatalysts, relevant explorations concerning AgI-based species are relatively rare, even though the excellent durability of AgI-based structures renders them attractive candidates for potential photocatalytic uses. By means of chemical reactions between AgNO3 and tetramethylammonium iodide (TMAI), and AgNO3 and tetrabutylammonium iodide (TBAI), we herein report that AgI structures with a sheet-like and a truncated-dodecahedron-like morphology, respectively, could be controllably synthesized via a surfactant-assisted fabrication protocol. In our synthesis systems, AgNO3 works as the silver source, while the TMAI and TBAI surfactants serve not only as an iodine source but also as a directing reagent for controllable fabrication. It has been demonstrated that our AgI structures could work as visible-light-energized photocatalysts towards the photodegradation of methyl orange. We find that compared to their sheet-like counterparts, the truncated-dodecahedron-like AgI architectures exhibit substantially boosted catalytic performances. Moreover, we disclose that our truncated-dodecahedron-like AgI-based species could display excellent photocatalytic stability, wherein their catalytic reactivity displays only trivial fluctuations under visible-light irradiation even after the photoreactions have been repeated 22 times continuously. Our work might not only introduce a facile protocol for the controllable synthesis of AgI structures but also pave an avenue for facile enhancement of their catalytic performances via morphology alterations.