Objective This study protocol aims to determine, using a rigorous approach in patients with bipolar disorder (BD) and non-seasonal major depressive episode (MDE), the characteristics of bright light therapy (BLT) administration (duration, escalation, morning and mid-day exposures) depending on the tolerance (hypomanic symptoms). Methods Patients with BD I or II and treated by a mood stabilizer are eligible. After 1 week of placebo, patients are randomized between either morning or mid-day exposure for 10 weeks of active BLT with glasses using a dose escalation at 7.5, 10, 15, 30 and 45 minutes/day. A further follow-up visit is planned 6 months after inclusion. Patients will be included by cohorts of 3, with at least 3 days of delay between them, and 1 week between cohorts. If none meet a dose limiting toxicity (DLT; i.e hypomanic symptoms), the initiation dose of the next cohort will be increased. If one patient meet a DLT, an additionnal cohort will start at the same dose. If 2 or 3 patients meet a DLT, from the same cohort or from two cohorts at the same dose initiation, the maximum tolerated dose is defined. This dose escalation will also take into account DLTs observed during the intra-subject escalation on previous cohorts, with a “Target Ceiling Dose”defined if 2 DLTs occured at a dose. Discussion Using an innovative and more ergonomic device in the form of glasses, this study aims to better codify the use of BLT in BD to ensure a good initiation and tolerance. Trial registration ClinicalTrials.gov Identifier: NCT03396744.