Aims To examine the relationship between breaks and patient safety in Korean hospitals and determine the mediating effect of missed nursing care on this relationship. Background Breaks during working hours can affect patient safety; however, few studies have examined the relationship between breaks and patient safety in hospitals and their findings were conflicting. Methods A cross-sectional online survey was conducted with 399 nurses in Korean hospitals. Multiple linear regression was used to explore the association between breaks, missed nursing care and patient safety. Model 4 of Hayes's (2018) and bootstrapping analysis were employed to identify the mediating effect of missed nursing care. Results Average break time per shift was about 15 min; most participants had breaks of less than 30 min. Missed nursing care was a complete mediator of the relationship between breaks and patient safety. Conclusion Break length has an indirect effect on patient safety, medication errors and falls with injury through missed nursing care. Implications for Nursing Management More discussion is needed to develop policy and mandatory regulations to ensure sufficient breaks and adequate nurse staffing to reduce missed nursing care and enhance patient safety.