OBJECTIVE: Modified thoracoabdominal nerve block with a perichondrial approach (M-TAPA) provides effective analgesia in the anterior and lateral thoracoabdominal regions. Previous studies have shown the efficacy of M-TAPA in laparoscopic surgery. The primary aim of this study was to investigate the efficacy of M-TAPA block in patients undergoing open major abdominal surgery. METHODS: This study was designed as a prospective, randomized, single-blind, controlled study. A total of 43 patients were included in the study. In group M-TAPA, the block was performed bilaterally at the end of the surgery. Local wound infiltration was performed on the control group. Postoperative analgesia was provided with patient-controlled intravenous morphine. When numeric rating scale (NRS) pain scores exceeded 4, rescue analgesia with tramadol was administered. The primary outcome of this study was to compare the 24-hour total morphine consumption. The secondary outcomes included comparing pain scores, rescue analgesia requirements, and patient satisfaction. RESULTS: Regarding our primary outcome, median morphine consumption during the first 24 hours was lower in the M-TAPA group [16 (14-18)] than in the control group [24.5 (19.5-27)] ( CONCLUSION: The M-TAPA block is an effective abdominal wall block that can be considered part of multimodal analgesia in open major abdominal surgery.