Introduction For peripheral nerve blocks, using either the liposomal formulation of bupivacaine or plain bupivacaine with epinephrine and dexamethasone as an adjuvant has been shown to improve postoperative pain scores. In a single-blinded, randomized controlled study of patients undergoing robotic-assisted thoracoscopic surgery, we determined if bupivacaine with epinephrine and dexamethasone was noninferior to liposomal bupivacaine mixed with plain bupivacaine when administered intraoperatively as an intercostal nerve block (INB). Methods A total of 34 patients undergoing robotic-assisted thoracoscopic surgery were randomized to receive one of two injectate mixtures during their intraoperative INB. Group LB was administered 266 mg of 13.3 mg/mL liposomal bupivacaine with 24 mL of 0.5% plain bupivacaine, while Group BD was given 42 mL of 0.5% bupivacaine with epinephrine and 8 mg of dexamethasone. The primary outcomes were mean postoperative numerical pain ratings and mean postoperative opioid analgesic requirements. Secondary outcomes included adjuvant pain medication consumption, hospital length of stay, and total opioid use in oral morphine equivalents. Results Group LB exhibited no significant difference in pain scores (p = 0.437) and opioid analgesic requirement (p = 0.095) within the 72-hour postoperative period when compared to Group BD. The median total postoperative opioid requirement was 90 mg in Group LB, compared to 45 mg in Group BD. There were no significant differences in the use of postoperative adjuvant pain medications (gabapentin, p = 0.833; acetaminophen, p = 0.190; ketorolac, p = 0.699). Hospital length of stay did not differ between the groups. Conclusions INBs with the addition of dexamethasone as an adjuvant to 0.5% bupivacaine with epinephrine provided noninferior postoperative analgesia compared to liposomal bupivacaine mixed with plain 0.5% bupivacaine.