The optimal regional technique for minimally invasive direct coronary artery bypass (MIDCAB) has yet to be determined. The aim of this study was to compare the efficacy of ultrasound-guided serratus anterior plane block (SAPB) with paravertebral block (PVB) and no block for controlling acute thoracotomy pain after robotic-assisted coronary artery bypass grafting (CABG).This is a retrospective study. Multiple variable regression analyses were performed.The study was performed as a single institution.All patients underwent robotic-assisted CABG.Data were analyzed from 197 patients during a 27-month period. Charts were abstracted manually to ascertain type of nerve block, age, gender, use of home opioids, use of adjuncts for opioid reduction, Society of Thoracic Surgeons predicted long length of stay (LOS), total opioid consumption during the 72 hours after surgery, and postoperative LOS. The authors' primary outcome was total morphine equivalents consumed during the first 72 hours after surgery. The secondary outcome was hospital LOS.Patients who received SAPB did not have significantly different opioid consumption than patients who had no block (p = 0.15), but it was increased significantly compared to patients administered PVB (PVB v SAPB catheter, p = 0.049; PVB v SAPB single shot, p = 0.049). There were no significant differences between groups in terms of postoperative LOS.These findings suggest SAPB might not cover adequately the incisional and tube pain associated with MIDCAB. If validated by prospective studies, these findings suggest that SAPB should be considered only for patients who are not candidates for PVB.