BACKGROUND: Individuals with substance use disorder (iSUD) often show diminished motivation toward treatment-seeking and adherence, resulting in a higher relapse rate, especially during the abstinence phase. A key cognitive correlate of substance use and treatment-seeking behavior is the ability to regulate emotion. While transcranial direct current stimulation (tDCS) shows potential for treating SUD, most studies have focused on craving or cognitive deficits. This randomized, placebo-controlled study examines the effects of 15 daily sessions of prefrontal tDCS on treatment motivation and cognitive emotion regulation in iSUD during the abstinence phase. METHODS: Thirty-two young male iSUDs (mean age= 22.80±1.92) were randomly assigned to the experimental (n=16) or placebo (n=16) groups. The experimental group underwent 15 sessions of anodal left and cathodal right dlPFC stimulation (2 mA, 20 min), while the placebo group received sham stimulation over the same period. Assessments of readiness, eagerness, motivation for treatment, and cognitive emotion regulation were conducted before and after the intervention. RESULTS: The active repeated prefrontal tDCS significantly boosted motivation for change and treatment in iSUD in comparison to sham tDCS. This intervention specifically improved participants' recognition of issues related to their substance use and reduced ambivalence about it. Additionally, active prefrontal tDCS enhanced adaptive cognitive emotion regulation while reducing maladaptive cognitive emotion regulation strategies in iSUD. CONCLUSIONS: Repeated prefrontal tDCS can help iSUD during the abstinence phase to improve adaptive emotion regulation strategies, thereby boosting motivation for treatment seeking. Up and downregulation of left and right dlPFCs is a promising approach for cognitively and motivationally preparing iSUD for treatment-seeking.