The Mental Capacity Act (MCA) 2005 introduced in 2007 aimed to revolutionise decision making processes in health and social care, ensuring a person-centred approach to those lacking mental capacity. Despite these intentions, research suggests a gap between the Act’s principles and the actual practice (The House of Lords Select Committee, 2014). This study explores this disparity by focusing on the understanding and application of the MCA in cases of self-neglect, a concern frequently identified in Serious Adult Reviews. As a practitioner researcher adopting a critical realist philosophy, the study conducted three focus groups involving nurses and social workers and a mixed group, with a total of thirty-three participants. Thematic analysis revealed four key themes. Firstly, the legal complexity emerged as a critical aspect influencing decision-making contexts. Secondly, relationships played a pivotal role, encompassing family dynamics, professional perception, and their impact on decision making. This led to the third theme, organisational features, highlighting how professionals operate within organisational structures affecting the assessment process and outcomes. Lastly, the study explored the participants’ learning experiences, emphasising the role of the training and professional qualification in shaping their preparedness for practice. While acknowledging limitations such as a small sample size and reliance on focus groups, the study offers a crucial starting point for further investigation. Ethnographic approaches are proposed for future research to delve deeper into the understanding and implementation of the MCA in practice. Observations of direct practice, supervision sessions and attendance at key meetings could unveil cultural and organisational factors influencing practitioners’ approaches to assessing mental capacity in cases of self-neglect. In conclusion, this study underlines the need for ongoing research to enhance the implementation of the MCA in practice. By identifying the multifaceted factors impacting decision making, practitioners and organisations can refine their approaches, ultimately fostering more effective support for individuals lacking mental capacity, particularly in cases where self-neglect is being considered.