Background: Despite scientific advances on pain measurement and intervention, pain management for infants has remained a challenge for health teams. This is because infants are not able to talk and defend themselves when they are in pain. Prevention of pain is important, not only because it is an ethical expectation, but also because repeated painful exposures can have harmful consequences. The aim of this study was to explore factors influencing neonatal pain management from the perspectives of nurses and physicians in a neonatal intensive care unit (NICU). Methods: A qualitative content analysis study was carried out. The participants were the nurses and physicians working in the NICU of Alavi medical training center in Ardabil, Iran. Twenty-five nurses took part in focus group discussions and five physicians attended private interviews. Four focus group discussions and five interviews were carried out until data saturation was ensured. Data analysis was performed using conventional content analysis. All the participants were provided with information about the purpose and the nature of the study, and provided informed consent. Results: Data analyses indicated two effective themes about barriers of implementation of infant pain management, namely "Individual Factors" and "Organizational Factors". The first theme consisted of the categories "knowledge of the personnel" and "commitment of the personnel". The second theme included three categories namely "pain control policy", "work environment condition" and "management issues". Conclusions: Our findings indicated that lack of educational courses, absence of an infant pain management policy, and management issues were the main obstacles in the way of implementation of infant pain management by nurses and physicians at the NICU. Therefore, strategies are required to reduce or remove these barriers.