Included in their extensive duties caring for hospitalized children, nurses are the frontline for pain assessment and treatment. Research has found that when nurses' assessments are compared with independent reports by the children or their parents, there are often differences. However, no studies have considered the contribution of analgesic medication consumption to this difference. The aim of this study, was to assess the concordance between the pain scores recorded independently by nurses, children, and their parents both before and 1 h after analgesic consumption. The trial was registered at ClinicalTrials.gov (NCT04306679) and was conducted in a post-operative inpatient facility. Following surgery, at first request of analgesic, the clinical nurses recorded the child's pain, as part of routine clinical practice. Within 10 min, the child recorded their pain level in a pain diary. At the same time, the parents separately reported their assessment of their child's pain. This process was repeated again 1 h later, when the nurses, as part of the clinical routine, recorded the children's level of post-medication pain. Forty-seven children ages 8-17 hospitalized for elective surgery in the General Pediatric Surgery, Orthopedics, Ear-Nose-Throat (ENT), and Oral and Maxillofacial (OM) Departments, and their parents, were included in the current report. The mean pain scores reported by the children were significantly higher than those reported by the nurses, both before (5.77±2.51 vs. 3.90±3.12 [mean ±SD], p <0.001) and 1 h after (3.37±2.48 vs. 0.92±2.08, p <0.001) analgesic consumption. No significant differences were found either before or after analgesic consumption in the NPS reported by the child and parent. Agreement between the NPS scores reported by the child and nurses was good before (ICC = 0.754, p <0.001) and only moderate 1 h after (ICC = 0.504, p = 0.017) analgesic consumption. Similarly, agreement between the NPS scores reported by the child and parents was good before (ICC = 0.855, p <0.001) and only moderate 1 h after (ICC = 0.722, p <0.001) analgesic consumption. While self-report measures remain the gold standard for pediatric pain care, the results of this study suggest that after analgesic administration, agreement between children's and nurses' assessments, and between children's and parents' assessments of pain deteriorated. Our results further confirm that proxy assessments recorded by parents are closer to their children's assessments than are those of nurses and should consequently be preferred especially after analgesic consumption. Copyright © 2022. Published by Elsevier Ltd.