Introduction: infants hospitalized in neonatology are inevitably and repeatedly exposed to pain. Premature infants are particularly vulnerable, because they are hypersensitive to pain and demonstrate diminished behavioral responses to pain. They are therefore at risk of developing short and long-term complications if pain remains untreated. Context: compared to acute pain, there is limited evidence in the literature on prolonged pain in infants. However, prevalence is reported as being between 20 and 40 percent. Objective: this single case study aimed to identify the bio-contextual characteristics of newborns who experienced prolonged pain. Methods: this study was carried out in the neonatal unit of a tertiary referral center in French-speaking Switzerland. A retrospective data analysis of seven infants’ profiles, who experienced prolonged pain, was performed using five different data sources. Results: the mean gestational age of the seven infants was 32 weeks. The main diagnoses included prematurity and respiratory distress syndrome. The total observations (N=55) showed that the participants had undergone on average 21.8 (SD 6.9) painful procedures that were estimated to be of moderate to severe intensity each day. Out of the 164 recorded pain scores (2.9 pain assessment/day/infant), 14.6 percent confirmed acute pain. Out of those experiencing acute pain, pain relief was given in 16.6 percent of them and 79.1 percent received no pain relief. Conclusion: this study highlighted the difficulty in managing pain in newborns who are exposed to numerous painful procedures. Pain in this population remains underevaluated and as a result undertreated. The results of this study showed that nursing documentation related to pain assessment is not systematic. Regular assessment and documentation of acute and prolonged pain are recommended. This could be achieved with clear guidelines on the Assessment/ Intervention/ Reassessment (AIR) cycle, with validated measures adapted to newborns. The adequacy of pain assessment is a pre-requisite for appropriate pain relief in newborns.