<p>This study establishes an electro-thermo-mechanically coupled crystal plasticity framework incorporating electroplastic effect to elucidate the fundamental mechanisms of current-assisted deformation in pure copper. In this framework, the thermal and athermal effects of electric current are independently described by the crystal plasticity constitutive model in terms of temperature and current density, respectively. The temperature field and current density distribution are obtained by solving the coupled heat conduction equation and current continuity equation. The model parameters are calibrated using experimental stress-strain responses of polycrystalline copper at different temperatures and current densities. Numerical simulations reveal that the thermal effects of electric current primarily manifest as shear modulus softening and enhanced thermal activation of dislocations, which have a relatively minor impact on flow stress. In contrast, the athermal effect significantly reduces both yield stress and hardening modulus by weakening the short-range and long-range resistances, leading to notable differences in flow stress during the work-hardening stage. Microstructural analysis shows that electric current alleviates stress concentrations caused by grain orientation differences and promotes more uniform distributions of dislocation density and slip deformation during plastic deformation. The proposed framework bridges the mesoscale dislocation slip and evolution with macroscale mechanical responses, providing critical insights for optimizing electrically-assisted forming processes through controlled electroplastic deformation.</p>