The objective of the present study was to evaluate morphine consumption and pain scores 24h postoperatively to compare the effects of a bilateral External Oblique Intercostal (EOI) block with those of a Modified Thoracoabdominal Nerve Block Trough Perichondrial Approach (M-TAPA) block in laparoscopic sleeve gastrectomy (LSG). Fifty-eight patients aged between 18 and 65years of with American Society of Anesthesiologists class II-III were included in this randomized, double-blinded study. Patients were assigned into two groups either EOI block or M-TAPA block. The primary outcome was cumulative morphine consumption within the first postoperative 24h. Secondary outcomes were numerical rating scale (NRS) scores at rest and during activity, QoR-15 Patient Questionnaire scores, incidence of postoperative nausea and vomiting (PONV), number of patients requiring rescue analgesic and antiemetics drugs, and complications. There was no statistically significant difference between the groups in terms of morphine consumption in the first 24h (EOI block; 10.74 ± 3.94mg vs. M-TAPA block; 11.67 ± 4.66mg, respectively). In addition, no significant difference between the two groups in the NRS and PONV scores, total QoR-15 scores, and the number of patients requiring rescue analgesics and antiemetics. EOI block and M-TAPA block showed similar effectiveness for morphine consumption within 24h postoperatively and in pain scores in LSG.