Triboelectric nanogenerators (TENGs) are a promising technology to convert mechanical energy to electrical energy based on coupled triboelectrification and electrostatic induction. With the rapid development of functional materials and manufacturing techniques, wearable and implantable TENGs have evolved into playing important roles in clinic and daily life from in vitro to in vivo. These flexible and light membrane‐like devices have the potential to be a new power supply or sensor element, to meet the special requirements for portable electronics, promoting innovation in electronic devices. In this review, the recent advances in wearable and implantable TENGs as sustainable power sources or self‐powered sensors are reviewed. In addition, the remaining challenges and future possible improvements of wearable and implantable TENG‐based self‐powered systems are discussed. Wearable and implantable triboelectric nanogenerators (TENGs) are developed for harvesting biomechanical energy, which can be used for sustainable power sources and self‐powered biosensors in vitro and in vivo. Research advances for these TENGs with different electric performance and the corresponding applications are discussed in detail. The perspectives on the challenges and solutions for these TENGs are proposed.