Background: Up to 60% of patients with bipolar disorder (BD) have a history of traumatic events, which is associated with greater episode severity, higher risk of comorbidity and higher relapse rates. Trauma-focused treatment strategies for BD are thus necessary but studies are currently scarce. The aim of this study is to examine whether Eye Movement Desensitization and Reprocessing (EMDR) therapy focusing on adherence, insight, de-idealisation of manic symptoms, prodromal symptoms and mood stabilization can reduce episode severity and relapse rates and increase cognitive performance and functioning in patients with BD. Methods/ design: This is a single-blind, randomized controlled, multicentre trial in which 82 patients with BD and a history of traumatic events will be recruited and randomly allocated to one of two treatment arms: EMDR therapy or supportive therapy. Patients in both groups will receive 20 psychotherapeutic sessions, 60 min each, during 6 months. The primary outcome is a reduction of affective episodes after 12 and 24 months in favour of the EMDR group. As secondary outcome we postulate a greater reduction in affective symptoms in the EMDR group (as measured by the Bipolar Depression Rating Scale, the Young Mania Rating Scale and the Clinical Global Impression Scale modified for BD), and a better performance in cognitive state, social cognition and functioning (as measured by the Screen for Cognitive Impairment in Psychiatry, The Mayer-SaloveyCaruso Emotional Intelligence Test and the Functioning Assessment Short Test, respectively). Traumatic events will be evaluated by The Holmes-Rahe Life Stress Inventory, the Clinician-administered PTSD Scale and the Impact of Event Scale. Discussion: The results of this study will provide evidence whether a specific EMDR protocol for patients with BD is effective in reducing affective episodes, affective symptoms and functional, cognitive and trauma