Dual-atom-site catalysts (DASCs) have garnered a lot of interest in the electrocatalysis community because of their atomic usage, stability, activity, and selectivity. This review systematically introduces the latest advancements of DASCs for electrocatalytic applications. Design principles of DASCs are first discussed, including atom-atom, atom-cluster, and atom-particle synergy. Then, rational modulation tactics are creatively proposed to speed up the construction of high-performance DASCs for uncovering structure–performance relationships. Moreover, advanced characterization techniques are provided to show the dynamic evolution of dual-atom sites throughout electrocatalysis. Finally, future challenges and perspectives are taken into account. This paper provides useful directions for a better understanding and design of DASCs for eco-friendly energy storage and conversion technologies.