Background: Recognizing and managing neonates' pain in the intensive care unit is challenging. Evidence shows that guidelines available in this area are not utilized effectively in practice. Purpose: To explore barriers to neonatal pain management in a neonatal intensive care unit.Methods: This was a qualitative study. Thirty-one nurses and physicians participated in the study. Data was collected through individual and focus group interviews. Data analysis was performed using conventional content analysis.Results: The barriers consisted of lack of holistic views towards neonates (exclusive concentration on treating the diseases, the neonate's inability to demand and protest verbally), subjective and arbitrary working (unorganized teamwork, lack of unified approach in pain-relieving, limited supervision for pain management), work overload (workload, physical and psychological strain on the caregivers), insufficient professional knowledge (Insufficient expertise in using pain assessment tools, Low importance of controlling environmental stimuli, Insufficient knowledge about pain management medication, and Considering patient's pain as expected).Conclusion: According to the professionals, the barriers to effective management of pain in neonates admitted to the intensive care unit in a developing country, are comprised of the individual, interpersonal, and organizational factors.Practice Implications: Investigation the barriers of optimal pain management in NICU can help to take the proper steps to improve the quality of service provided. Education of care providers, designing and implementation of a unified neonatal-based pain management program, and proper organizational supervision could improve neonatal pain management. Also, physical and emotional support of care workers is essential for more quality performance.