Non-enzymatic hydrogen peroxide sensor was constructed and designed by electrodeposition of silver nanoparticles on a modified glassy carbon electrode (GCE) with an electrochemically reduced graphene oxide (ERGO) and cobalt oxide (Co3O4) film. The characterization of Ag NPs/Co3O4/ERGO/GCE was carried out by scanning electron microscopy, cyclic voltammetry, and chronoamperometry. The result of scanning electron microscopy demonstrated Ag NPs were dispersed on the Co3O4/ERGO composite. Electrochemical measurements revealed that the Ag NPs electrodeposition on the Co3O4 film provides an electrode with boosted current of reaction, sensitivity, and outstanding stability. The sensor displayed superior linearity in the concentration range of 50 μM to 1.1 mM with a detection limit of 0.84 μM (S/N=3) and showed high sensitivity (2950 μA mM−1 Cm−2).