Purpose: The Newborn Infant Parasympathetic Evaluation (NIPE) monitor is an objective, non-invasive tool for the assessment of pain in children <2 years-of-age. The aim of this study was to perform an objective and detailed analysis of the intraoperative pain in infants undergoing open inguinal hernia repair (OIHR) using the NIPE monitor. Methodology: This prospective observational study included neonates and infants undergoing elective OIHR under general anaesthesia with a caudal block. The NIPE monitor was connected to the electrocardiogram monitor with continuous monitoring performed intraoperatively. The NIPE index was recorded at different intraoperative steps and the median NIPE (NIPEm) index was calculated for the entire procedure; NIPE index ranges from 0-100, lower values indicate greater levels of pain, values <50 indicate severe pain. Data reported as median [range]. Results: There were 30 infants recruited. NIPEm was 77.00 [46.00-91.50], indicating an overall level of comfort throughout the procedure for all patients. Similarly, no intraoperative steps had a NIPEm of <50: skin incision (64.00 [29.00-89.00]), external oblique incision (79.00 [22.00-86.00]), spermatic cord delivery (70.00 [32.00-95.00]), hernial sac isolation (64.00 [35.00-97.00]), sac suturing (78.00 [49.00-90.00], testis repositioning (74.50 [33.00-93.00]), external oblique closure (73.00 [50.00-92.00]), and skin closure (73.00 [40.00-92.00]). Conclusion: General anaesthesia with caudal block during OIHR appears to provide adequate cover for pain. The most painful steps identified during the procedure were skin incision, spermatic cord delivery and hernial sac isolation. These findings could be used to guide the intraoperative pain management by the anaesthetic team.