Children with pectus excavatum are treated with surgical repair in a procedure known as minimally invasive repair of pectus excavatum (MIRPE). MIRPE causes considerable postoperative pain, resulting in the administration of a substantial dose of opioids. This study aimed to identify perioperative factors that influence the requirement for opioids in children undergoing MIRPE. Retrospective data from children who underwent MIRPE were analyzed. A multimodal analgesic protocol was implemented with a continuous wound infiltration system and administration of non-opioid analgesics. Intravenous opioid analgesics were administered if the pain score was greater than 4. The cumulative opioid use was assessed by calculating the morphine equivalent dose at 6, 24, and 48 h after surgery. Perioperative factors affecting the postoperative opioid use were identified with multiple linear regression analyses. This study included 527 children aged 3–6 years, with a mean age of 3.9 years. Symmetrically depressed chest walls, a lower Haller index, and a lower revised depression index were found to be associated with decreased postoperative opioids. Boys required higher opioid doses than girls. Longer pectus bars (10 inches versus 9 inches) were associated with increased opioid use. Severity indices, gender, and the length of pectus bars influence postoperative opioid requirement in children undergoing MIRPE surgery with multimodal analgesia.