Purpose: Preventing missed care is important in neonatal intensive care units (NICUs) due to neonates’ vulnerabilities. This study examined missed care and its influencing factors among NICU nurses.Methods: Missed care among 120 Korean NICU nurses was measured using a cross-culturally adapted online questionnaire. The frequency of missed care for 32 nursing activities and the significance of 23 reasons for missed care were collected.Results: All participants had missed at least 1 activity, missing on average 19.35 activities during a typical work-day. The most common missed item was “provide developmental care for the baby”. The most common reason for missed care was “emergency within the unit or deterioration of one of the assigned patients”. The final regression model explained 9.6% of variance in missed care. The average daily number of assigned patients receiving inotropes or sedation over the last month influenced the total number of missed care items.Conclusion: Missed care was affected by nurses’ workload related to the number of patients taking medication. Frequently missed activities, especially those related to developmental care, require patience and time, conflicting with safety prioritization and inadequate working conditions. NICU nurses’ working conditions should be improved to ensure adequate time for nursing activities.