INTRODUCTION:We are conducting a randomised controlled trial (Promoting Activity, Independence and Stability in Early Dementia and Mild Cognitive Impairment - PrAISED 2) to test the effectiveness of an intervention to promote activity and independence amongst people with mild cognitive impairment and early dementia. A process evaluation is needed to determine how the intervention works. This protocol outlines the rationale, aims, objectives and methods of the process evaluation. METHODS:The process evaluation will use a mixed-methods design and comprise two studies: An implementation study, examining the process through which PrAISED 2 is delivered, and a study on the mechanisms of impact and context, focussing on the mediating mechanisms that contribute to study outcomes. Integration of separate analyses of quantitative and qualitative data will provide a holistic view of how the PrAISED 2 intervention works. CONCLUSION:Results from this process evaluation will further the understanding of the factors that can impinge on the success of complex interventions. This will represent invaluable information for researchers undertaking further research around behaviour change among people with cognitive impairment and dementia.