The objective was to evaluate the effects of a multicomponent dyadic intervention on the cognitive functioning of people with dementia living at home in a randomized controlled trial. People with dementia and their family caregivers (n = 111) were randomly assigned to 8 home-based sessions including physical exercise and support or a minimal intervention consisting of monthly written information bulletins and monthly phone calls. Memory, executive functioning (EF), and attention were assessed at baseline, and after 3 (postmeasurement) and 6 months (follow-up). Data were analyzed by using generalized estimating equations (GEE). A small, significant effect was found on attention. No effects were found on memory and EF. Finding only a small significant effect might be explained by the ineffectiveness of the intervention, but also by moderate treatment adherence or a lack of room for improvement because half of the people with dementia were already receiving care in a day care facility.