BACKGROUND Children with microtia complain of severe postoperative pain during early postoperative days after rib cartilage harvest for auricular reconstruction. The purpose of this study was to evaluate the effects of preventive donor site wound analgesia by intercostal nerve block (ICNB) and catheter-based infusion of local analgesics on postoperative pain after rib cartilage graft for auricular reconstruction in children with microtia. METHODS In this prospective randomized study, 66 children underwent postoperative pain control using either preventive ICNB followed by catheter-based infusion (33 patients, study group) or intravenous (IV) analgesia alone (33 patients, control group). ICNB was performed under direct vision by the surgeon by injecting 0.5% bupivacaine into each of the three intercostal spaces before perichondrial dissection. Catheters were placed in three subchondral spaces before wound closure, and 0.5% bupivacaine was infused every 12 h for 48 h postoperatively. Pain degrees were recorded every 4 h during the first 48 postoperative hours using a visual analogue scale. RESULTS The study group showed significantly lower mean pain scores of the chest at rest (3.7 vs. 5.1, p = 0.001), the chest during coughing (4.3 vs. 5.8, p = 0.006), and the ear (3.0 vs. 4.1, p = 0.001) than the control group. The amount of use of rescue IV ketorolac was smaller in the study group (p = 0.026) than in the control group. No side effects related to the intervention were noted. CONCLUSIONS Preventive ICNB followed by catheter-based infusion is effective and safe in postoperative pain relief in rib cartilage graft for auricular reconstruction. (The clinical trial registration number: WHO ICTRP, apps.who.int/trialsearch (KCT0001668)).