A microwave filter is important to determine the performance of a wearable communication system. However, the materials used in existing microwave filters require sophisticated and expensive fabrication processes. Moreover, they are not compatible with flexible and wearable platforms. In this study, a novel strategy for realizing a tunable fabric microwave filter (TFMF) by taking advantage of the spoof surface plasmon polariton (SSPP) structure and using organic electrochemical transistors (OECTs) is presented, which are lightweight and exhibit excellent mechanical flexibility and deformability. The TFMF is manufactured using fabric materials, and the OECT is printed to serve as a state‐changing material. The developed TFMF exhibits excellent flexibility, high planar integration and improved wearing comfort. Furthermore, the operating frequency of the TFMF with well‐designed gradient structures and multi‐state dispersion characteristics can be effectively tuned by applying different voltage sequences. To the best of the authors’ knowledge, this is the first tunable microwave filter designed for use in wearable systems. The measurements of scattering parameters and data transmission with a communication system based on the TFMF demonstrate a feasible pathway for enhancing the performance of wearable wireless communication systems.