Familiarity is important for persons living with dementia who participate outside home. When familiarity is challenged, such participation may be difficult. This ethnographic study clarifies how familiarity is experienced by persons with dementia in performing activities and visiting places, and how familiarity contributes to maintaining participation outside home. Nine participants were interviewed in their home and while visiting familiar places. Data were content analysed using a constant comparative method. The findings suggest that persons with dementia experience familiarity as continuous and whole, through occurrences that support personal territories. Landmarks and objects enhance the experience of familiarity. Familiarity that is continuously challenged may render participation outside home fragile.