Postoperative pain treatment affects immediate and long-term outcomes in children undergoing cardiac surgery. Opioids, as part of multimodal analgesia, are effective in treating pain, however, they can be disadvantageous due to adverse side effects. Therefore, we assessed whether the local anesthetic bupivacaine as a parasternal nerve block in children post-cardiac surgery is an effective adjunct to pain management. This was a retrospective cohort study of all patients who underwent cardiothoracic surgery via median sternotomy at a large children's hospital between November 2011 and February 2014 with and without bupivacaine following the introduction of perioperative bupivacaine in late 2012 on a single unit. 62 out of 148 patients (age 3-17 years) who received bupivacaine demonstrated decreased postoperative opioid use. Within one day of surgery, patients who received bupivacaine required, on average, 0.57 mg/kg (95% CI, 0.46 to 0.68) of total morphine equivalent compared to 0.93 mg/kg (95% CI, 0.80 to 1.06) for patients who did not receive bupivacaine. This difference was statistically significant after adjusting for potential confounders (-value = 0.002). Length of stay and intubation were shorter on average among patients who received bupivacaine, but these differences were not statistically significant after adjusting for potential confounders. The study results seem to suggest that the perioperative administration of bupivacaine may reduce opioid usage among children post-cardiotomy.