To examine a novel moderated-mediation model, investigating whether personal accountability moderates the link between nurse workload and missed nursing care and whether missed nursing care mediates the association between workload and moral distress. Nested diary study. Data spanning from February 2019 to February 2023 were collected from 137 nurses working in various inpatient wards in two medium-sized hospitals. Nurses reported care given to specific patients on three to five occasions across different shifts, establishing nurse-patient dyads. Validated measures of missed nursing care, personal accountability, moral distress and workload were analyzed using mixed linear models to test the nested moderated-mediation model. Under high workload conditions, nurses with higher personal accountability reported lower frequencies of missed nursing care compared to those with lower personal accountability. In contrast, under low workload conditions, personal accountability did not significantly influence missed nursing care occurrences. Furthermore, the interaction between workload and personal accountability indirectly affected nurses' moral distress through missed nursing care. Specifically, higher personal accountability combined with lower missed nursing care contributed to reduced levels of moral distress among nurses. The study highlights accountability's dual role-safeguarding against care omissions and influencing nurses' moral distress amid rising workload pressures. Cultivating a culture of accountability within healthcare settings can serve as a protective factor against the negative effects of workload on patient care quality and nurse psychological distress, highlighting the need for organizational interventions to promote accountability among nursing staff. By recognizing accountability's pivotal role, organizations can implement targeted interventions fostering accountability among nurses, including training programs focused on enhancing responsibility/ownership in care delivery and creating supportive environments prioritizing accountability to achieve positive patient outcomes. The study has adhered to STROBE guidelines. No patient or public contribution.