Supported metal nanostructures are the most extensively studied heterogeneous catalysts, benefiting from easy separation, regeneration and affordable cost. The size of the supported metal species is one of the decisive factors in determining the activity of heterogeneous catalysts. Particularly, the unsaturated coordination environment of metal atoms preferably act as the active centers, minimizing these metal species can significantly boost the specific activity of every single metal atom. Single-atom catalysts/catalysis (SACs), containing isolated metals atomically dispersed on or coordinated with the surface of a support material, represent the ultimate utilization of supported metals and maximize metal usage efficiency. Graphene, a two-dimensional star material, exhibiting extraordinary physical and chemical properties, has been approved as an excellent platform for constructing SACs. When atomically dispersed metal atoms are strongly anchored on the graphene surface, featuring ultra-high surface area and excellent electronic properties, SACs offer a great potential to significantly innovate the conventional heterogeneous catalysis, especially in the field of electrocatalysis. In this review, a detailed discussion of graphene-supported SACs, including preparation approaches, characterization techniques and applications on typical electrocatalytic reactions is provided. The advantages and unique features of graphene-supported SACs as efficient electrocatalysts and the upcoming challenges for improving their performance and further practical applications are also highlighted.