This thesis examines the foundations and effects of the BigMove intervention, an innovative approach to person-centred, integrated, and community-based care for people with physical and mental health conditions. The intervention aims to improve participants’ functioning, capabilities, and quality of life while fostering behaviour change. As the number of adults living with multimorbidity continues to grow, healthcare systems face increasing challenges in providing adequate care. Current interventions, often targeting specific diseases and their associated health-related risk behaviours, frequently fail to meet the needs of people with multimorbidity. A person-centred, integrated, community-based intervention that goes beyond isolated, disease-oriented approaches may improve outcomes beyond narrow disease-specific aspects. Over the past decades, two frameworks have significantly contributed to the transition towards more integrated and person-centred care: the International Classification of Functioning, Disability, and Health (ICF) and the Capability Approach (CA). The joint use of these frameworks has three advantages; (1) it provides the opportunity to increase patients’ influence and choice regarding their functioning and to give them a more equal position in the delivery of care, (2) it enables an evaluation of functionings and capabilities from the perspective of patients; and (3) it provides a basis for recording self-perceived functioning and evaluation of goals suitable for use in research and quality improvement. A practical example is presented through a unique e-health application used in the intervention that allows a person to self-assess, record, and evaluate their self-perceived functioning, as well as formulate related goals and action plans. The theoretical frameworks reflected in the intervention are the Capability Approach (CA) and Self-Determination Theory. Essential elements of the intervention are motivational interviewing, functional goal setting using the ICF, cognitive behavioural therapy, enjoyment, group support and physical activity. The design combines individual sessions and group sessions. Furthermore, the intervention incorporates collaboration between healthcare professionals. Examining data on participants' self-perceived functioning, goals, and action plans before and after experiencing at least 120 days demonstrated that the application can be used to record self-perceived functioning, goals, and action plans and capture changes over time. The evaluation of outcomes on self-perceived health, quality of life, coping behaviour, and social and mental functioning after 120 days in the intervention, indicated significant improvements. The observed changes can be considered clinically relevant improvements. Based on the theoretical perspectives and the findings of this thesis, a novel model to capture the process of behaviour change in the intervention is presented: the Model of Complex Dynamic Behaviour Change. Finally, recommendations for policy, practice, education, and future research are made. More emphasis should be placed on integrating relational autonomy and freedom of choice into care pathways. The use of the ICF to assess self-perceived functioning, goals, and action plans could provide a novel method of evaluating person-centred care as well as provide information for policymakers to shape future policies. This thesis offers valuable insights for future development and evaluation of interventions for individuals with multimorbidity.