Recently, heterogeneous single-atom catalysts (SACs) have attracted enormous attention in electrochemical applications owing to their advantages of high metal utilization, well-defined active sites, tunable selectivity, and excellent activity. To avoid the aggregation of atomically dispersed metal sites, an appropriate support has to be adopted to reduce the surface free energy of catalysts. Graphene with a high surface area, outstanding conductivity, and unique electronic properties has generally been utilized as the substrate for SACs. Moreover, the correlations between metal-support interactions and the electrocatalytic performance at the atomic scale can be studied on graphene-supported single-atom catalyst (G-SAC) nanoplatforms. In this review, we start from an overview of the synthetic methods for G-SACs. Subsequently, several advanced and effective characterization techniques are discussed. Then, we present a comprehensive summary of recent progress in G-SACs for a variety of electrochemical applications. Finally, we present challenges for and an outlook on the development of G-SACs with outstanding catalytic activity, stability, and selectivity.