Abstract Background The prevalence of diagnosed chronic obstructive pulmonary disease (COPD) in the UK is 1.8%, although it is estimated that this represents less than half of the total disease in the population as much remains undiagnosed. Case finding initiatives in primary care will identify people with mild disease and symptoms. The majority of self-management trials have identified patients from secondary care clinics or following a hospital admission for exacerbation of their condition. This trial will recruit a primary care population with mild symptoms of COPD and use telephone health coaching to encourage self-management. Methods/Design In this study, using a multi-centred randomised controlled trial (RCT) across at least 70 general practices in England, we plan to establish the effectiveness of nurse-led telephone health coaching to support self-management in primary care for people who report only mild symptoms of their COPD (MRC grade 1 and 2) compared to usual care. The intervention focuses on taking up smoking cessation services, increasing physical activity, medication management and action planning and is underpinned by behavioural change theory. In total, we aim to recruit 556 patients with COPD confirmed by spirometry with follow up at six and 12 months. The primary outcome is health related quality of life using the St Georges Respiratory Questionnaire (SGRQ). Spirometry and BMI are measured at baseline. Secondary outcomes include self-reported health behaviours (smoking and physical activity), physical activity measured by accelerometery (at 12 months), psychological morbidity, self-efficacy and cost-effectiveness of the intervention. Longitudinal qualitative interviews will explore how engaged participants were with the intervention and how embedded behaviour change was in every day practices. Discussion This trial will provide robust evidence about the effectiveness of a novel telephone health coaching intervention to promote behaviour change and prevent disease progression in patients with mild symptoms of dyspnoea in primary care. Trial registration Current controlled trials ISRCTN06710391 .