Although batteries are a highly popular energy source in biosensors, batteries can be an economic limitation for low-cost sensing applications and pose significant challenges in miniaturization, biocompatibility, and disposal. To surmount such issues, “self-powered sensors” gain the spotlight thanks to their energy harvesting from the environment through embedded miniaturized systems. In this review, the recent developments in self-powered devices are summarized with a specific focus on the integration of supercapacitors with sensors and biosensors. The working principles of microsupercapacitors, fabrication methods, their integration with biosensors, and their ultimate applications (i.e., biomedical monitoring and analytical biomarker detection) are described. Different energy harvesting systems are summarized and their integration with self-powered sensors or biosensors is highlighted. The limitations and challenges of the existing approaches and the future of supercapacitor-integrated sensing systems are also critically discussed.