Background: Postoperative pain management after pacemaker insertion routinely requires opioid agents, nonsteroidal anti-inflammatory drugs, or paracetamol. However, interest in opioid-sparing multimodal pain management to minimize postoperative narcotic use has increased recently. This study aimed to assess the pectoral nerve (PECS) block versus standard treatment on postoperative pain control and opioid consumption in pediatric patients after transvenous subpectoral pacemaker insertion.Method: In this randomized controlled study, 40 pediatric patients underwent transvenous subpectoral pacemaker insertion with either congenital or postoperative complete heart block. Patients were randomly assigned to two groups: Group C (control) received conventional analgesic care without any block and Group P (pectoral) received a PECS block. Demographics, procedural variables, postoperative pain, and postoperative opioid consumption were compared between the two groups. Results: In children undergoing transvenous subpectoral pacemaker insertion, the PECS block was associated with a longer procedure time; however, the cumulative dose of fentanyl and atracurium was reduced and the hemodynamic profile was superior in Group P compared with Group C intraoperatively. Postoperatively, the PECS block was associated with lower postprocedural pain scores, which was reflected by the longer interval before the first call for rescue analgesia and lower postoperative morphine consumption, without an increase in the rate of complications. Conclusion Ultrasound-guided PECS blocks are associated with a good intraoperative hemodynamic profile, reduced postoperative pain scores, and lower total opioid consumption in children undergoing transvenous subpectoral pacemaker placement.