Single atom catalysts (SACs) have attracted considerable attention due to their unique structures and excellent catalytic performance, especially in the area of catalysis science and energy conversion and storage. In recent years, SACs have emerged as a new type of sensing material for constructing electrochemical sensors (ECSs), presenting excellent sensitivity, selectivity, and stability. Herein, we review the recent advances of SACs in electrochemical sensing and discuss the status quo of current SAC-based ECSs. Specifically, the fundamentals of SAC-based ECSs are outlined, including the involved central metal atoms and various supports of SACs in this field, the detection mechanisms, and improving strategies of SAC-based ECSs. Moreover, the important applications of SAC-based ECSs are listed and classified, covering the detection of reactive oxygen and nitrogen species, environmental pollutants, disease biomarkers, and pharmaceuticals. Last, based on abundant reported cases, the current conundrums of SAC-based ECSs are summarized, and the prediction of their future developing trends is also put forward.