ABSTRACT: BACKGROUND:People with chronic obstructive pulmonary disease (COPD) are at increased risk of depression and anxiety, which greatly reduces their quality of life and is associated with worse outcomes; but these psychological co-morbidities are under-recognised and undertreated in COPD patients. Pulmonary rehabilitation (PR) improves mood for up to 6 months but health practitioners under-refer, and patients commonly fail to attend/complete PR. Research suggests that complex non-pharmacological interventions, including both psychological and exercise components, may reduce anxiety and depression in COPD. We have developed a tailored, cognitive behavioural approach (CBA) intervention for patients with COPD and co-morbid anxiety and/or depression ('TANDEM'), which precedes and optimises the benefits of currently offered PR. We hypothesise that such a psychological intervention, delivered by supervised, trained respiratory healthcare professionals, will improve mood in patients with mild to moderate anxiety and/or depression and encourage uptake and completion of PR. METHODS:We will conduct a multi-centre, pragmatic, randomised controlled trial of the TANDEM intervention compared to usual care across the Midlands, London, the South East and Bristol, UK. We will train healthcare professionals familiar with COPD to deliver the manualised, tailored, face-to-face, one-to-one intervention weekly for 6-8?weeks. We will recruit 430 participants from primary, community and secondary care with confirmed COPD and moderate to very severe airflow limitation, who are eligible for assessment for PR, and who screen positive for symptoms of mild/moderate depression and/or anxiety using the Hospital Anxiety and Depression scale (HADS). Participants will be randomised 1.25:1 (intervention: usual care). The co-primary outcomes are the HADS anxiety and depression subscale scores at 6?months; participants will be followed up to 12?months. Secondary outcomes include uptake and completion of PR and healthcare resource use. There will be a parallel process evaluation and a health economic evaluation. DISCUSSION:The TANDEM intervention has the potential to optimise the unrealised synergy between a psychological intervention and PR. The CBA sessions will precede PR and target individuals' cognitions, behaviours and symptoms associated with anxiety and depression to decrease psychological morbidity and increase effective self-management amongst patients with COPD. TRIAL REGISTRATION:ISRCTN, ID: ISRCTN59537391. Registered on 20 March 2017. Protocol version 6.0, 22 April 2018.