Catalysts with isolated active sites have demonstrated preferable H2O2 productivity via the 2e− oxygen reduction reaction, but their synthesis procedures are usually sophisticated, with only a few isolated sites generated. Here, we employ perovskite as a platform for facilely constructing isolated active sites with dense populations to produce H2O2. As a proof of concept, a silver niobate catalyst, where the Ag sites are isolated by the NbO6 octahedra with an atomic distance (dAg–Ag) larger than 0.39 nm, is demonstrated to show outstanding H2O2 productivity at both low and high currents. Combining theoretical calculations, chemical/electrochemical surface species tuning methods, and in situ transmission electron microscopy, the isolated Ag sites in AgNbO3 are determined to be the active sites for the H2O2 production. This study offers an initial exploration of the perovskite structure as a platform for constructing isolated active sites, paving the way for its potential application in more fields.