This study examined the postoperative analgesic efficacy of single-injection pectoral fascial plane (PECS) II blocks compared to paravertebral blocks for elective robotic mitral valve surgery. A single-center retrospective study that reported patient and procedural characteristics, postoperative pain scores, and postoperative opioid use for patients undergoing robotic mitral valve surgery. This investigation was performed at a large quaternary referral center. Adult patients (age ≥18) admitted to the authors' hospital from January 1, 2016, to August 14, 2020, for elective robotic mitral valve repair who received either a paravertebral or PECS II block for postoperative analgesia. Patients received an ultrasound-guided, unilateral paravertebral or PECS II nerve block. One hundred twenty-three patients received a PECS II block, and 190 patients received a paravertebral block during the study period. The primary outcome measures were average postoperative pain scores and cumulative opioid use. Secondary outcomes included hospital and intensive care unit lengths of stay, need for reoperation, need for antiemetics, surgical wound infection, and atrial fibrillation incidence. Patients receiving the PECS II block required significantly fewer opioids in the immediate postoperative period than the paravertebral block group, and had comparable postoperative pain scores. No increase in adverse outcomes was noted for either group. The PECS II block is a safe and highly effective option for regional analgesia for robotic mitral valve surgery, with demonstrated efficacy comparable to the paravertebral block.