Background: The global aging poses nursing care challenges, with an increasing demand for complex care among older individuals. In Sweden, the 80+ age group is projected to grow by 50% from 2020 to 2030, necessitating a comprehensive examination of factors influencing nursing home residents' health and quality of life (HRQoL). Within this landscape, person-centred care (PCC) has demonstrated its central role in elevating the health and HRQoL of nursing home residents. Aim: To investigate relationships between leadership, person-centred care (PCC), resident health (cognitive impairment, neuropsychiatric symptoms, daily living activities), and resident quality of life (QoL) and changes over five years. Design: This study employs a repeated cross-sectional design with data from staff, residents and managers. Data collection occurred in 2014 and 2019, using reliable scales to assess health-related quality of life (HRQoL), cognitive impairment, neuropsychiatric symptoms, PCC and leadership. Methods: Data collection included 4,831 residents at baseline 2014 and 3,894 residents at follow-up in 2019. Additionally, 3,665 staff (baseline) and 2,985 staff (follow-up) participated in 2014. Organizational data covered 172 nursing homes at baseline and 202 at follow-up. Robust statistical analyses, including descriptive statistics and regression modelling, explored relationships between person-centred care, leadership and residents' health and quality of life.  Results: No association was found between leadership and resident health or HRQoL. Significant correlations emerged between person-centred care and resident HRQoL and other health outcomes. This underscores the role of PCC for nursing home residents. Conclusion: This study reveals the interplay between leadership, PCC, resident health, and QoL in nursing homes. While leadership may not directly impact resident outcomes, person-centred care seems to beneficially impact HRQoL and other health outcomes. Prioritizing PCC practices in nursing homes may increase residents' quality of life. Further research is warranted to explore specific PCC elements contributing to improved QoL among nursing home residents.