BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with significant morbidity, mortality and healthcare costs. Beta blockers are well-established drugs widely used to treat cardiovascular conditions. Observational studies consistently report that beta blocker use in people with COPD is associated with a reduced risk of COPD exacerbations. The bisoprolol in COPD study (BICS) investigates whether adding bisoprolol to routine COPD treatment has clinical and cost-effective benefits. A sub-study will risk stratify participants for heart failure to investigate whether any beneficial effect of bisoprolol is restricted to those with unrecognised heart disease. METHODS: BICS is a pragmatic randomised parallel group double-blind placebo-controlled trial conducted in UK primary and secondary care sites. The major inclusion criteria are an established predominant respiratory diagnosis of COPD (post-bronchodilator FEV1 < 80% predicted, FEV1/FVC < 0.7), a self-reported history of ≥ 2 exacerbations requiring treatment with antibiotics and/or oral corticosteroids in a 12-month period since March 2019, age ≥ 40 years and a smoking history ≥ 10 pack years. A computerised randomisation system will allocate 1574 participants with equal probability to intervention or control groups, stratified by centre and recruitment in primary/secondary care. The intervention is bisoprolol (1.25 mg tablets) or identical placebo. The dose of bisoprolol/placebo is titrated up to a maximum of 4 tablets a day (5 mg bisoprolol) over 4-7 weeks depending on tolerance to up-dosing of bisoprolol/placebo-these titration assessments are completed by telephone or video call. Participants complete the remainder of the 52-week treatment period on the final titrated dose (1, 2, 3, 4 tablets) and during that time are followed up at 26 and 52 weeks by telephone or video call. The primary outcome is the total number of participant reported COPD exacerbations requiring oral corticosteroids and/or antibiotics during the 52-week treatment period. A sub-study will risk stratify participants for heart failure by echocardiography and measurement of blood biomarkers. DISCUSSION: The demonstration that bisoprolol reduces the incidence of exacerbations would be relevant not only to patients and clinicians but also to healthcare providers, in the UK and globally. TRIAL REGISTRATION: Current controlled trials ISRCTN10497306 . Registered on 16 August 2018.