Mental and cognitive disorders (MCD) negatively affect the incidence and prognosis of coronary heart disease (CHD). Medical guidelines recommend the appropriate management of comorbid MCD in patients with CHD, yet there is evidence that the implementation in primary care is not always adequate. We present the protocol for a pilot study that aims to develop a minimally invasive intervention and evaluate its feasibility in the primary care setting to improve the identification and management of comorbid MCD in patients with CHD. The study consists of two consecutive parts and will be carried out in Cologne, Germany. Part 1 comprises the development and tailoring of the intervention, which is guided by qualitative interviews with primary care physicians (PCPs,n= 10), patients with CHD and MCD and patient representatives (n= 10). Part II focuses on the implementation and evaluation of the intervention inn= 10 PCP offices. Changes in PCP behaviour will be analysed by comparing routine data in the practice management system six months before and six months after study participation. In addition, we will explore the influence of organisational characteristics and perform a socio-economic impact assessment. The outcomes of this mixed-method study will inform the feasibility of a PCP-based intervention to improve quality of care in patients with CHD and comorbid MCD.