During the last decade online interventions have emerged as a promising approach for patients with mild/moderate depressive symptoms, reaching at large populations and representing cost-effective alternatives. The main objective of this double-blind, randomized controlled trial is to examine the efficacy of an internet-based self-management tool (iFightDepression) for mild to moderate depression as an add-on to treatment as usual (TAU) versus internet-based psychoeducation plus TAU. A total of 310 participants with major depression disorder (MDD) will be recruited at four different mental-health facilities in Spain. Participants will be randomly allocated to one of two study arms: iFightDepression (iFD) tool + TAU vs. internet-based psychoeducation + TAU. Both interventions last for 8 weeks and there is a 12 weeks follow up. The primary outcome measure is changes in depressive symptoms assessed with the Hamilton Depression Rating Scale. Additionally, pre-post interventions assessments will include socio-demographic data, a brief medical and clinical history and self-reported measures of depressive symptoms, quality of life, functional impairments and satisfaction with the iFD tool. iFightDepression is an easy-prescribed tool that could increase the efficacy of conventional treatment and potentially reach untreated patients, shortening waiting lists to receive psychological treatment. Confirming the efficacy of the iFD internet-based self-management tool as an add-on treatment for individuals with mild to moderate depression will be clinically-relevant. Registration number . December 4, 2014.