The oblique subcostal transversus abdominis plane (OSTAP) block has been described as an effective analgesic method for upper abdominal surgery. We evaluated the postoperative analgesia of the OSTAP block and compared it with that of the transversus abdominis plane (TAP) block in patients undergoing laparoscopic cholecystectomy (LC). Patients scheduled for elective LC were randomized to receive either standard care or to undergo an OSTAP or TAP block. All blocks were performed with ultrasound guidance, and 20 mL of 0.375% ropivacaine was injected bilaterally. The postoperative pain score and consumption of rescue analgesics were evaluated. The OSTAP block reduced postoperative verbal numerical rating scale pain scores (median [Interquartile range, IQR]) compared to standard care at 10 min (2 [1-4] vs. 7 [5-8]), 30 min (2 [1-5] vs. 6 [5-8]), 1 h (2 [1-3] vs. 5 [4-6]), and 3 h (2 [2-3] vs. 4 [3-5]). Pain scores were also lower in the OSTAP group than in the TAP group at 10 min (2 [1-4] vs. 4 [2-6]), 1 h (2 [1-3] vs. 3 [3-4]), 3 h (2 [2-3] vs. 3 [3-4]), 6 h (2 [2-3] vs. 3 [3-5]), and 24 h (1 [1-2] vs. 2 [2-3]) postoperatively. The total fentanyl requirement was reduced in the OSTAP group (p = 0.005). The OSTAP block can provide better analgesia than the TAP block or standard care during the postoperative 24 h period in patients undergoing LC.