We present surface reconstruction‐induced C−C coupling whereby CO₂ is converted into ethylene. The wurtzite phase of CuGaS_2. undergoes in situ surface reconstruction, leading to the formation of a thin CuO layer over the pristine catalyst, which facilitates selective conversion of CO₂ to ethylene (C₂H₄). Upon illumination, the catalyst efficiently converts CO₂ to C₂H₄ with 75.1 % selectivity (92.7 % selectivity in terms of R_electron) and a 20.6 μmol g⁻¹ h⁻¹ evolution rate. Subsequent spectroscopic and microscopic studies supported by theoretical analysis revealed operando‐generated Cu²⁺, with the assistance of existing Cu⁺, functioning as an anchor for the generated *CO and thereby facilitating C−C coupling. This study demonstrates strain‐induced in situ surface reconstruction leading to heterojunction formation, which finetunes the oxidation state of Cu and modulates the CO₂ reduction reaction pathway to selective formation of ethylene.