Despite a growing population of chronically and acute critically ill neonatal and pediatric patients, there were few published articles related to moral distress as experienced by nurses caring for these patients.The aim of this study was to define moral distress based on the perceptions and experiences of neonatal and pediatric critical care nurses.A qualitative descriptive study using focus group methodology was undertaken. All nurses with 2 or more years of experience from the 4 neonatal and pediatric intensive care units in a large 404-bed urban pediatric hospital located in the northeast were invited to attend 1 of 15 audio-recorded focus groups lasting 60 to 90 minutes. Once data were transcribed, conventional content analysis was used to develop the definition and categories of moral distress.Nurse participants defined moral distress as "patient care situations where there is a mismatch or incongruity between expected behaviors of the nurse and his/her personal values/beliefs in the neonatal/pediatric critical care setting." The 2 overarching categories that emerged from the data were patient-focused factors and nurse-focused factors.Understanding how neonatal and pediatric critical care nurses define moral distress and what contributes to its development is foundational to developing targeted strategies for nursing support and education, with the goal of creating a culture of moral resiliency.