Background <p>Retro-superior costotransverse ligament space block (RSSB) is a new variant of thoracic paravertebral block (TPVB), while subcostal transversus abdominis plane block (TAPB) is a commonly used analgesic technique in laparoscopic surgery. This study aimed to compare the effects of RSSB and TAPB on postoperative analgesia and quality of postoperative recovery in patients with gastric cancer undergoing laparoscopic gastrectomy. We hypothesized that RSSB provides more comprehensive analgesia and promotes postoperative recovery than TAPB.</p> Methods <p>This prospective randomized controlled trial enrolled 60 patients with gastric cancer undergoing laparoscopic gastrectomy. Eligibility criteria included age 18–85 years, body mass index (BMI) 18.5–28&#xa0;kg/m², American Society of Anesthesiologists (ASA) physical status I–III, and scheduled elective laparoscopic gastrectomy. Patients were assigned to two groups in a 1:1 random manner. The RSSB group received bilateral injections of 40 mL 0.375% ropivacaine at the T7–8 level; the TAPB group received the same volume and concentration of ropivacaine (40 mL total, 20 mL per side) along the subcostal anterior axillary line. The primary outcome was the area under the curve (AUC) of numeric rating scale (NRS, 0 to 10) during 24&#xa0;h postoperatively.</p> Results <p>A total of 52 patients were included in the analysis. NRS-AUC within 24&#xa0;h postoperatively was significantly lower in the RSSB group compared to the TAPB group (mean (SD) AUC: 48.3 (24.0) vs. 75.4 (35.7), <i>P</i> = 0.002). The neural block spread range in the RSSB group was significantly wider than in the TAPB group (mean (SD) superficial spread segments: 5.2 (2.1) vs. 3.0 (0.7), <i>P</i> &lt; 0.001). Meanwhile, the time to first Patient-controlled analgesia (PCA) bolus request was markedly prolonged in the RSSB group compared with the TAPB group (mean (SD) 480.6 ± 385.8 vs. 249.1 ± 256.4, <i>P</i> = 0.034). Additionally, within the first 24&#xa0;h postoperatively, the RSSB group scored higher on the Quality of Recovery-15 (QoR-15) scale than the TAPB group (mean (SD): 122.4 (7.1) vs. 115.0 (16.4), <i>P</i> = 0.039). No statistically significant differences were observed between the two groups in other secondary outcome measures.</p> Conclusions <p>This study demonstrates that RSSB provides better postoperative analgesia than subcostal TAPB and improves early postoperative recovery quality in patients undergoing laparoscopic gastrectomy.</p> Trial registration <p>ChiCTR2500096679. Registered 1 February 2025 (prospectively registered).</p>