Personal, multifunctional, and smart electronic devices/systems are indispensable components of the internet of things for modern information collection and exchange, which play a key role in facilitating the development of human civilization. Traditional technique for powering these sensor nodes mainly relies on batteries, which may not be favorable owing to the limited battery lifetime, large sensor population, wide distribution, as well as the potential of environmental detriment. Extricated from external power sources, triboelectric nanogenerators (TENGs) based active sensors have been extensively spread into a variety of fields for self-powered high-performance sensing, featured as being lightweight, extremely cost-effective, and environmentally friendly. In this article, current progress of TENGs as smart sensors for self-powered touch detection, vibration and acoustic sensing, biomedical applications, as well as human-machine interfacing, has been comprehensively reviewed, from aspects of materials usage, device fabrication to practical applications. The latest representative achievements regarding the TENG based self-powered sensing systems were also systematically presented. In the end, some perspectives and challenges for the TENG based self-powered smart sensors were also summarized.