Study objective: A lateral mini-thoracotomy approach to cardiac surgery causes severe and complicated postoperative pain compared to the sternotomy approach. In this study we assessed the benefits and risks of intermittent bolus erector spinae plane block (ESPB) via a catheter for patients who underwent cardiac surgery through a lateral mini-thoracotomy. Design: A propensity score-matched retrospective cohort study. Setting: University hospital. Patients: 452 consecutive patients that underwent cardiac surgery through a lateral mini-thoracotomy from 2018 to 2020. Interventions: Patients who received intermittent bolus ESPB through a catheter for 3 days (ESPB group, n = 93) were compared with patients who did not receive any regional anesthesia (Control group, n = 174) after propensity score matching. Measurements: The primary endpoint was postoperative in-hospital cumulative opioid consumption (calculated as oral morphine milligram equivalents, MME). The secondary outcomes were intraoperative sufentanil doses, therapeutic use of antiemetic, pulmonary infection (assessed using a modified clinical pulmonary infection score, CPIS), durations of ICU and hospital stays, and ESPB related/unrelated complications. Main results: There is a lower oral MME in the ESPB group, 266 +/- 126 mg in the ESPB group vs. 346 +/- 105 mg in the control group (95% CI-113 to-46; P < 0.01). Fewer patients received therapeutic antiemetic agents in the ESPB group (30% vs. 42%, odds ratio 0.58; 95% CI 0.34 to 0.99; P = 0.04). The modified CPIS in the ESPB group is lower: 1.4 +/- 0.9 vs. 2.0 +/- 1.0 (95% CI-0.9 to-0.3; P < 0.01) on postoperative day 1; 1.6 +/- 0.9 vs. 2.0 +/- 0.9 (95% CI-0.7 to-0.2; P < 0.01) on postoperative day 2. The observed complications associated with ESPB include pneumothorax (1%), staxis around stomas (5%), hypotension (1%), catheter displacement (3%), and catheter obstruction (2%). None of the patients had any adverse outcomes. Conclusion: Intermittent bolus ESPB is relatively safe and correlated with a reduction in the use of opioids and antiemetics for cardiac surgery through a lateral mini-thoracotomy.