Electrochemical CO₂ conversion to methane requires a multi-step hydrogenation and involves a complex cascade reaction. It would be vital to achieve efficient catalytic performance if one could construct tandem active centers towards the multiple intermediates. Herein, we provided a pyrolysis-free synthetic strategy to fabricate monoatomic-nanocluster Cu dual active centers for highly selective methanation of CO₂. Expectedly, the tandem active centers realized the stepwise electrocatalytic reduction, during which the atomic Cu increased the dissociation of H₂O while the Cu nanoclusters with a high electron density promoted the activation of CO₂, synergistically accelerating the hydrogenation of *CO into *CHO, suppressing H₂ generation and favoring the formation of CH₄. The as-prepared catalysts demonstrated a superior Faradaic efficiency of 78.8% with a large partial CH₄ current density of 111.5 mA·cm⁻² at −1.3 V vs. RHE, providing an avenue for the rational design and controllable synthesis of highly selective and active Cu-based CO₂ reduction reaction (CO₂RR) catalysts.