To generate, test and refine programme theories that emerged from a rapid realist review investigating practising UK Nurses' and Midwives' experiences of effective leadership strategies during the COVID-19 pandemic. The realist review of literature generated six tentative theories of healthful leadership practices reflecting, working with people's beliefs and values; being facilitative; multiple means of communication and; practical support. The review yielded little insight into the actual impact of the leadership approaches advocated. A realist study, informed by person-centredness using mixed-methods. Online survey (n = 328) and semi-structured interviews (n = 14) of nurses and midwives across the UK in different career positions/specialities. Quantitative data analysed using descriptive statistics and exploratory factor analysis. Framework analysis for qualitative data using context (C), mechanism (M), outcome (O) configurations of the tentative theories. Three refined theories were identified concerning: Visibility and availability; embodying values and; knowing self. Healthful leadership practices are only achievable within organisational cultures that privilege well-being. Leaders should intentionally adopt practices that promote well-being. 'Knowing self' as a leader, coaching and mentoring practice development is important for leadership development. Nurses who feel valued, heard, cared for and safe are more likely to remain in clinical practice. Job satisfaction and being motivated to practice with confidence and competence will impact positively on patient outcomes. The study addresses the role of leadership in developing healthful workplace cultures. The main findings were six leadership practices that promote healthful cultures. The research will have an impact on strategic and clinical leaders, nurses and midwives. This study used EQUATOR checklist, RAMASES II as reporting standards for realist evaluations. No patient or public contribution.