In this study, we have fabricated a dual-signal sensor for H₂O₂ determination based on 2D Cu-MOFs decorated with Ag NPs. A novel polydopamine (PDA) reduction method was utilized to reduce [Ag(NH₃)₂]⁺ to highly dispersed Ag NPs in situ without other reductive agents, and Cu-MOF@PDA-Ag was obtained. For the electrochemical sensor, the Cu-MOF@PDA-Ag modified electrode exhibits outstanding electrocatalytic properties toward H₂O₂ reduction with a high sensitivity of 103.7 μA mM⁻¹ cm⁻², a wide linear range from 1 μM to 35 mM and a low detection limit of 2.3 μM (S/N = 3). Moreover, the proposed sensor shows good feasibility in an orange juice sample. For the colorimetric sensor, colorless 3,3′,5,5′-tetramethylbenzidine (TMB) can be oxidized by the Cu-MOF@PDA-Ag composite in the presence of H₂O₂. A Cu-MOF@PDA-Ag catalysis-based colorimetric platform is further established for the quantitative analysis of H₂O₂ ranging from 0 to 1 mM with a lower detection limit of 0.5 nM. Importantly, such a dual-signal method for the detection of H₂O₂ could potentially have wide practical applications.