BACKGROUND: There is currently insufficient evidence for the clinical effectiveness and cost-effectiveness of psychological therapies for post-stroke depression. OBJECTIVE: To evaluate the feasibility of undertaking a definitive trial to evaluate the clinical effectiveness and cost-effectiveness of behavioural activation (BA) compared with usual stroke care for treating post-stroke depression. DESIGN: Parallel-group, feasibility, multicentre, randomised controlled trial with nested qualitative research and a health economic evaluation. SETTING: Acute and community stroke services in three sites in England. PARTICIPANTS: Community-dwelling adults 3 months to 5 years post stroke who are depressed, as determined by the Patient Health Questionnaire-9 (PHQ-9) or the Visual Analogue Mood Scales 'Sad' item. Exclusions: patients who are blind and/or deaf, have dementia, are unable to communicate in English, do not have mental capacity to consent, are receiving treatment for depression at the time of stroke onset or are currently receiving psychological intervention. RANDOMISATION AND BLINDING: Participants were randomised (1 : 1 ratio) to BA or usual stroke care. Randomisation was conducted using a computer-generated list with random permuted blocks of varying sizes, stratified by site. Participants and therapists were aware of the allocation, but outcome assessors were blind. INTERVENTIONS: The intervention arm received up to 15 sessions of BA over 4 months. BA aims to improve mood by increasing people's level of enjoyable or valued activities. The control arm received usual care only. MAIN OUTCOME MEASURES: Primary feasibility outcomes concerned feasibility of recruitment to the main trial, acceptability of research procedures and measures, appropriateness of baseline and outcome measures, retention of participants and potential value of conducting the definitive trial. Secondary feasibility outcomes concerned the delivery of the intervention. The primary clinical outcome 6 months post randomisation was the PHQ-9. Secondary clinical outcomes were Stroke Aphasic Depression Questionnaire - Hospital version, Nottingham Leisure Questionnaire, Nottingham Extended Activities of Daily Living, Carer Strain Index, EuroQol-5 Dimensions, five-level version and health-care resource use questionnaire. RESULTS: Forty-eight participants were recruited in 27 centre-months of recruitment, at a recruitment rate of 1.8 participants per centre per month. The 25 participants randomised to receive BA attended a mean of 8.5 therapy sessions [standard deviation (SD) 4.4 therapy sessions]; 23 participants were allocated to usual care. Outcome assessments were completed by 39 (81%) participants (BA,  = 18; usual care,  = 21). Mean PHQ-9 scores at 6-month follow-up were 10.1 points (SD 6.9 points) and 14.4 points (SD 5.1 points) in the BA and control groups, respectively, a difference of -3.8 (95% confidence interval -6.9 to -0.6) after adjusting for baseline PHQ-9 score and centre, representing a reduction in depression in the BA arm. Therapy was delivered as intended. BA was acceptable to participants, carers and therapists. Value-of-information analysis indicates that the benefits of conducting a definitive trial would be likely to outweigh the costs. It is estimated that a sample size of between 580 and 623 participants would be needed for a definitive trial. LIMITATIONS: Target recruitment was not achieved, although we identified methods to improve recruitment. CONCLUSIONS: The Behavioural Activation Therapy for Depression after Stroke trial was feasible with regard to the majority of outcomes. The outstanding issue is whether or not a sufficient number of participants could be recruited within a reasonable time frame for a definitive trial. Future work is required to identify whether or not there are sufficient sites that are able to deliver the services required for a definitive trial. TRIAL REGISTRATION: Current Controlled Trials ISRCTN12715175. FUNDING: This project was funded by the NIHR Health Technology Assessment programme and will be published in full in ; Vol. 23, No. 47. See the NIHR Journals Library website for further project information.