Background: There has been a growing global focus on the value of person-centredness in healthcare, research, policy, and education. Research and theoretical developments in this area have demonstrated the pivotal role nurses and midwives play in the delivery and development of person-centred practice. However, to evaluate and improve person-centred practice, nurses and midwives need to have access to relevant data pertaining to care delivery. There is an abundance of mobile health (mHealth) apps currently available, collecting copious amounts of healthcare data. Yet very few apps are designed to capture data relating to the patient experience or person-centredness. There is also limited evidence available reporting how nursing and midwifery staff use mHealth apps and the data collected by them to inform person-centred practice change. Aim and research questions: The aim of this PhD study was to explore how nurses and midwives generate and use data from an mHealth app to improve person-centred practice. To achieve this, three research questions were posed: How do nurses and midwives generate data to evidence person-centred care using an mHealth app? How do nurses and midwives engage with evidence/data to inform person-centred practice change? How does working with this kind of evidence influence nurses and midwives to be person-centred in their practice? Methods: The study used participatory action research methodology, underpinned by the Person-centred Nursing Framework (McCormack & McCance, 2021), and informed by Practice Development principles. Nursing and midwifery staff on six clinical units engaged in three action cycles using an mHealth app that captured data pertaining to the patient experience. Participants were supported to use the app, and the data collected by it, to evaluate and develop person-centred practice. To understand staff experience and the influence that working with the data had on understanding of person-centredness, a pre-post survey was undertaken along with qualitative interviews. Findings: The findings revealed that, although mHealth apps can be efficient and effective tools for data collection and storage, nurses and midwives require support to use them and understand the data collected. This is best achieved through collaborative and inclusive approaches such as facilitation and working with clinical teams in cycles over time. The findings of this study demonstrated that using mHealth apps and the data collected by them in this way results in person-centred practice improvements affecting patients and staff. Engaging nurses and midwives in collecting and reflecting on data pertaining to the patient experience not only resulted in