Nanomaterials have gained burgeoning attention in various fields including biomedicine and energy during last decades. The traditional strategies to research nanomaterials can only record the average characteristics of ensemble materials, which may lead to analysis deviation. The emergence of single-nanoparticle analysis techniques has tackled the problem, but their low analysis speed and sensitivity limit their further applications. Electrochemiluminescence (ECL) is an electrochemical reactions-dependent luminescence process without external light sources. Coupled with a microscopy configuration, a novel imaging methodology ECL microscopy (ECLM) has been developed. ECLM, due to its distinctive imaging mode, holds considerable potential in the field of single-nanoparticle research. This chapter will initially present an overview of some common ECL nanoemitters, including the basic principles of their ECL emission and their current applications. The next section will discuss diverse applications of ECLM in studying single nanoparticles. Finally, we will summarize the challenges and outline the prospects for further development of single-nanoparticle ECLM technique.