Implantable bioelectronics capable of electrophysiological monitoring intimately interfacing with biological tissue have provided massive information for profound understanding of biological systems. However, their invasive nature induces a potential risk of acute tissue damage, limiting accurate and chronic monitoring of electrophysiological signals. To address this issue, advanced studies have developed effective strategies to engineer the soft, flexible device using preclinical animal models. In addition, the optional but innovative approaches to improve the device's function have been also explored. Herein, these strategies satisfying essential and supplemental requirements for engineering implantable bioelectronics are summarized. Three types of implantable devices, classified by their structural designs, are introduced to describe the approaches using suitable strategies for their specific purpose. In conclusion, the further advancement of engineering implantable bioelectronics addresses the remaining challenges. Such advancements have the potential to contribute to enhanced functionality, encouraging a more delicate understanding of the physiology of biological systems and further broadening the applicability of implantable bioelectronics in the field of biomedical technology.