Abstract <p>In this work, the slurry electrolysis (SE) of a complex polymetallic sulfide secondary concentrate (CPSSC) in the FeCl₃–HCl–NaCl system and the anodic mechanism were investigated. The experimental results showed a significant increase in Cu extraction efficiency (e.g., 91.3% at 0.14 A and 85&#xa0;°C in 11&#xa0;h, saving 4–13&#xa0;h, compared with the atmospheric leaching time in acidic ferric system) by using SE, increasing current/temperature, and decreasing particle content. Moreover, the HCl consumption was decreased. The proportions of contribution of direct electro-oxidation caused by CPSSC particle collisions with the anode, indirect electro-oxidation caused by FeCl₃, indirect electro-oxidation induced by X₂ (X = O and Cl), and chemical dissolution caused by H⁺ to Cu extraction at 0.14 A were 0.081 (or 0.119 at 0.03 A where no X₂ evolved), 0.526, 0.315, and 0.078, respectively in 11&#xa0;h, indicating weak direct collisions (although their proportions non-monotonically changed with time) and chemical dissolution. Moreover, the results confirmed that Fe³⁺ and X₂ played key roles in Cu leaching. With increasing time/current, the role of X₂ became prominent for leaching enhancement rather than the collision, although there was a synergistic effect between H⁺, Fe²⁺/Fe³⁺, and X₂. The low anodic currents related to collisions before X₂ evolution in linear sweep voltammetry curves without FeCl₃ and the low proportions (0.032–0.100) determined from the collision kinetic analysis also verified such a weak direct collision electro-oxidation reaction. The products obtained after SE were S⁰-rich residues and cathodic high-purity Cu (96.6 at.%), verified by XRD and SEM–EDS.</p> Graphical Abstract <p></p>