Background: This study investigated whether a personalized life story book and rummage box enhanced well-being and led to changes in behaviour for people with Down syndrome (DS) who have dementia. Materials and Methods: A randomized single case series design was used with five participants who had DS and a diagnosis of dementia. Participants were invited to take part in three conditions at random (i) life story book, (ii) rummage box and (iii) no-intervention condition. Results: The two reminiscence conditions were significantly associated with enhanced well-being as compared to the no-intervention condition. However, for one participant, the life story book was associated with significantly higher well-being, while for another participant, the rummage box was associated with significantly higher well-being, suggesting some participants may prefer one method over another. Conclusions: Personalized life story books and rummage boxes are associated with higher levels of well-being for people with DS and dementia.