Multi-atom cluster catalysts have turned out to be novel heterogeneous catalysts with atomic dispersion for electrochemical energy applications. Beyond a simple combination of single-atom catalysts, they could offer boosted activity as a result of the synergistic effects between adjacent atoms. Meanwhile, the multiple active sites in the catalytic center may render them versatile binding modes toward adsorbates and provide an opportunity for catalyzing complex reactions with diverse products. Herein, a comprehensive review of the recent development of multi-atom cluster catalysts for electrochemical energy applications is provided. Specifically, the origin of synergistic effects in multi-atom cluster catalysts and related modulation methods are illustrated and summarized. The introduction of multi-atom cluster catalysts to circumvent the scaling relationships as well as their potential for developing new descriptors is then discussed. Subsequently, the methods for fabricating multi-atom cluster catalysts and related characterization techniques are reviewed. This is followed by the discussion of their application in key electrochemical reactions such as water splitting, oxygen reduction, and carbon dioxide/monoxide reduction, as well as the real-time techniques for their mechanistic study. Finally, the future challenges and opportunities concerning the improvement of multi-atom cluster catalysts are outlined, which are essential to make such electrocatalysts viable for electrochemical energy conversion.