Ocean research currently relies heavily on bulky bioelectronic tags and sensory telemetry networks for data collection. Therefore, in this study, a compact and flexible waterproof bioelectronic tag with a kirigami (paper cutting)‐based design for underwater conductivity, temperature, depth, and strain sensing is designed and evaluated. Unlike invasive bioelectronic tags, the kirigami bioelectronic tag can be attached to robotic fish or aquatic animals without harming the host. The kirigami‐based design facilitates excellent stretchability and reduces stress within the sensor, thus inhibiting crosstalk induced by movement during multimodal sensing. A working bioelectronic tag is fabricated and tested. Notably, the performance of the kirigami sensors shows very little degradation even after >1000 stretching cycles. Specifically, the multimodal bioelectronic tag demonstrated a wide working pressure range of 0–5.0 MPa, and the kirigami design effectively suppressed signal coupling. The kirigami‐based bioelectronic tag is applied to a robotic dolphin and underwater environmental parameters and detailed movement parameters, such as swing angle, swing frequency, and typical gestures are detected simultaneously with high sensitivity and accuracy. Therefore, the device can be applied to a broad range of applications in various fields such as behavioral biology, ocean informatics, and underwater robotics.