Abstract Background Depression in later life is a common mental disorder with a prevalence rate of between 3% and 35% for minor depression and approximately 2% for Major Depressive Disorder (MDD). The most common treatment modalities for MDD are antidepressant medication and psychological interventions. Recently, Behavioral Activation (BA) has gained renewed attention as an effective treatment modality in MDD. Although BA is considered an easy accessible intervention for both patients and health care workers (such as nurses), there is no research on the effectiveness of the intervention in inpatient depressed elderly. The aim of study, described in the present proposal, is to examine the effects of BA when executed by nurses in an inpatient population of elderly persons with MDD. Methods/design The study is designed as a multi-center cluster randomized controlled trial. BA, described as The Systematic Activation Method (SAM) will be compared with Treatment as Usual (TAU). We aim to include ten mental health care units in the Netherlands that will each participate as a control unit or an experimental unit. The patients will meet the following criteria: (1) a primary diagnosis of Major Depressive Disorder (MDD) according to the DSM-IV criteria; (2) 60 years or older; (3) able to read and write in Dutch; (4) have consented to participate via the informed consent procedure. Based on an effect size d = 0.7, we intend to include 51 participants per condition (n = 102). The SAM will be implemented within the experimental units as an adjunctive therapy to Treatment As Usual (TAU). All patients will be assessed at baseline, after eight weeks, and after six months. The primary outcome will be the level of depression measured by means of the Beck Depression Inventory (Dutch version). Other assessments will be activity level, mastery, costs, anxiety and quality of life. Discussion To our knowledge this is the first study to test the effect of Behavioral Activation as a nursing intervention in an inpatient elderly population. This research has been approved by the medical research ethics committee for health-care settings in the Netherlands (No. NL26878.029.09) and is listed in the Dutch Trial Register (NTR No.1809).