OBJECTIVE: The aim of the study was to identify components of the COM-B (capability, opportunity, motivation and behaviour) model that influences behaviour to modify dietary patterns in 40-55-year-olds living in the UK, in order to influence the risk of cognitive decline in later life. DESIGN: This is a qualitative study using the COM-B model and theoretical domains framework (TDF) to explore beliefs to adopting the Mediterranean-DASH Intervention for Neurodegenerative delay (MIND) diet. SETTING: Northern Ireland. PARTICIPANTS: Twenty-five participants were recruited onto the study to take part in either a focus group or an interview. Participants were men and women aged between 40 and 55 years. Participants were recruited via email, Facebook and face to face. RESULTS: Content analysis revealed that the main perceived barriers to the adoption of the MIND diet were time, work environment, taste preference and convenience. The main perceived facilitators reported were improved health, memory, planning and organisation, and access to good quality food. CONCLUSIONS: This study provides insight into the personal, social and environmental factors that participants report as barriers and facilitators to the adoption of the MIND diet among middle-aged adults living in the UK. More barriers to healthy dietary change were found than facilitators. Future interventions that increase capability, opportunity and motivation may be beneficial. The results from this study will be used to design a behaviour change intervention using the subsequent steps from the Behaviour Change Wheel.