BackgroundImpulsivity is a core feature of borderline personality disorder (BPD) and is closely related to suicide risk and destructive and aggressive behaviors. Although transcranial direct current stimulation (tDCS) has shown its promising effects as an intervention to modulate impulsivity, no study has explored its potential regarding BPD.Methods/designThis is a multicenter, crossover, double-blind study comparing active versus sham tDCS (2 mA, 30 min), applied over the dorsolateral prefrontal cortex for five consecutive days in 50 BPD patients. Participants will be assessed for impulsivity, depressive symptoms, and suicide risk. The main efficacy criteria on reduction of impulsivity will be the amplitude variation of one specific evoked potential detected by electroencephalography (EEG) during the balloon analogue risk task. Baseline measures will be compared to scores obtained immediately after sessions, then 12 and 30 days later.DiscussionThis study investigates the safety and effects of tDCS, which may have a significant impact on impulsivity in patients with BPD and may be useful to reduce risky behaviors.Trial registrationClinicalTrials.gov, NCT03498937. Registered on 17 April 2018.