Understanding a person’s life story can transform dementia care by promoting a person-centered approach. Documented life stories help staff to personalize care, but further research is needed to understand their construction and usage in care practice. The aim of this study was to explore assistant nurses’ experiences of life story documentation and their practical applications in dementia care practice. Five semi-structured focus groups were conducted, and data were analyzed using qualitative content analysis. The findings consisted of five themes: “Ensuring timing and accessibility when constructing a documented life story,” “Recognizing template limitations in capturing a comprehensive view of the person,” “Refining life story quality and understanding through ongoing dialogues,” “Building connection and support through insights from documented life stories,” and “Harmonizing life histories with evolving care needs in practice.” Our findings highlight the importance of a dynamic and inclusive approach to life story documentation that goes beyond rigid templates. Accessible and well-documented life stories can empower nursing staff to provide responsive and personalized care, enhancing the dignity and quality of life of people living with dementia.