The agency of a person with young onset dementia (YOD) changes owing to individual symptoms, uncertainty about the speed of progression and the severity of YOD. Dementia usually greatly interrupts life and reduces agency. Previous studies show that some people and families integrate and cope with dementia better than others. This study aimed to find out how YOD changes the agency of the person who has it and what family members’ role is in forming their agency. The data were collected in Finland in semi-structured interviews with 14 people with YOD and 15 family members, about a year after the diagnosis. These two data sets were analysed with a narrative method, actantial analysis. A wide variety of elements, both human and non-human factors, were found to promote and undermine agency. It was found that people with YOD need both integrity and flexibility to reconstruct their own agency. Resources support them in this process of reconstruction, and hinderers interrupt the process. This combination of integrity and flexibility, resources and hinderers, generates how people with YOD recount the future, the aims they set and how they reconstruct their agency. Other people, especially family members, are part of this dynamic process and when their relationship is cohesive, the agency of both parties increases. The participants used ideal and burdensome storylines to narrate factors that supported or interrupted their agency. Based on our findings, narrating one’s situation is, for coping, not only a means but its very basis.