AbstractThe emergence of organic electrochemical transistors (OECTs) has opened a new era of printable electronics and bioelectronics, due to their unique advantages including innately superior transconductance and biocompatibility. Despite the foreseeable advancements available from their further implementations in fundamental logic circuitry, however, insufficient operation speeds and short compatibilities to scaling‐down have so far hindered advanced integrations other than biosensing and biosignal amplifications. Here, a 3D‐construction‐dependent operational analysis of OECTs is reported, with which an all‐vertical architectural design enabled unprecedentedly high operating speed and a facile expansion to large‐area and high‐density 3D crossbar arrays. A simple vertical channel architecture completed with solid‐state Ag/AgCl top‐gate electrodes enables an ultrafast redistribution of ions within channels, yielding a state‐of‐the‐art operation frequency reaching 12 MHz V−1. Various printed logic circuit arrays, including NOT, NAND, and NOR gates, with high stability and reproducibility.