Self‐powered sensing technologies are increasingly sought for intelligent and autonomous marine environmental monitoring. A Faraday cage‐enabled triboelectric nanogenerator (FC‐TENG) is developed by incorporating a FeCoCrNiAl alloy powder layer, enabling efficient harvesting of low‐frequency mechanical energy. The quasi‐enclosed conductive architecture mimics a Faraday cage, effectively confining electrostatic charges and suppressing edge‐induced dissipation, thereby enhancing charge retention. Compared to single‐metal triboelectric layers, the FC‐TENG exhibits 4.86‐, 3.57‐, and 2.76‐fold increases in open‐circuit voltage ( V OC , 1276.27 V), short‐circuit current ( I SC , 63.69 μA), and transferred charge ( Q SC , 29.55 nC), respectively. Its hydrophobic surface further ensures environmental robustness and stable output under humid conditions. With an optimized load resistance of 60 MΩ, the FC‐TENG device achieves a peak power of ~4.08 mW and reliably powers LED arrays and environmental sensors, while enabling efficient energy storage across a wide frequency range. Furthermore, a wave‐driven FC‐TENG system integrated with wireless communication and visual feedback modules enables real‐time marine motion monitoring without external power. This work introduces the Faraday cage–inspired triboelectric device based on microspherical alloy powder, offering enhanced charge retention, humidity tolerance, and dual‐mode functionality in power generation and marine wave sensing. The proposed strategy provides a robust and scalable architecture for future self‐powered systems operating in harsh environments.