The rapid and accurate detection of hydrogen peroxide (H2O2) has recently been a fascinating research topic in electro-chemical sensing. Herein, spinel CuMn2O4 nanoflakes were synthesized through coprecipitation and pyrolysis methods and then dropcoated onto the surface of a bare glassy carbon electrode (GCE), successfully generating an enzymatic-free electrochemical sensor (CuMn2O4/GCE) for good amperometric detection ability of H2O2. In comparison with the reported spinel AB(2)O(4)-based electrocatalysts in a phosphate buffer solution, the CuMn2O4/GCE sensor exhibits a high sensitivity of 3.420 A M-1 cm(-2) and a low detection limit of 12 nM. This excellent sensing performance is mainly derived from the inherent porous structure and the large electrochemical active area of spinel CuMn2O4 nanoflakes, as well as the synergistic effect between Cu and Mn that facilitates electron transfer and increases active sites. Especially, the high contents of Cu+ and Mn3+ ions in the nanocatalyst are useful for promoting the capture and reduction of trace H2O2. In addition, the CuMn2O4/GCE sensor presents a satisfactory recovery in monitoring H2O2 derived from rat serum, commercial milk, and disinfectors, indicating its potential applications in related environmental, food, and biological fields.