The Mental Capacity Act (MCA) was fully implemented in England and Wales in October 2007 and has relevance for the care home sector through its focus on decision-specific assessments of capacity. This article reports on research that forms part of a five year programme exploring evidence-based interventions in dementia and this article draws on part of the research that was designed to identify issues relating to implementation of the Act. Specific research questions for this study pertain to staff abilities to incorporate a new legal framework addressing mental capacity into care of people with dementia. Qualitative interviews with 32 staff in one group of care homes in Southern England demonstrated that, regardless of knowledge of MCA, the daily working ethos of staff appeared to be within the remit of Act. Training could therefore continue to build on these principles. However, considerable variation in understanding of terms and principles of the MCA was found. Few participants were aware of specific legislative points and offered ‘common sense’ explanations for their actions and decision-making. This level of knowledge may not meet regulators’ requirements or the needs of residents.