Background: Deep neuromuscular block (NMB) has been increasingly utilized in laparoscopic oncologic surgery, but its role in reducing intraoperative opioid requirement has yet to be investigated. Opioid in cancer patients is related with immunosuppression. Surgical pleth index (SPI) quantifies nociception. We investigated the effects of deep NMB on remifentanil requirements in the elderly patients undergoing laparoscopic gastrectomy under SPI-guided anesthesia. Methods: In this randomized controlled trial, the elderly patients aged 60–85 years who underwent laparoscopic gastrectomy for gastric cancer were included. Arrythmia, peripheral vascular disease and chronic opioid user were excluded. The patients (n = 60) were randomly allocated into deep (n = 30) or moderate (n = 30) NMB groups between December 2019 and December 2020. The moderate NMB group was maintained as Train-of-four count 1-2 during surgery and revered using neostigmine 50 ug/kg after the end of surgery. The deep NMB group was maintained as post-tetanic count 1-2 and reversed with using sugammadex 4 mg/k. The remifentanil dose was assessed during intubation, from skin incision until CO₂ insertion, and pneumoperitoneum. Results: Demographic, hemodynamic and operational data were similar between two groups, except rocuronium dose. The remifentanil doses administered for tracheal intubation and during time from skin incision until CO₂ insertion were similar (P = 0.412 and P = 0.649). In addition, total dose of remifentanil administered during pneumoperitoneum was not significantly different between two groups (P = 0.315), which remains non-significant when adjusted by weight, duration or both (P = 0.603, P = 0.146, and P = 0.389). Consequently, total dose of remifentanil administered during anesthesia was not different (P = 0.247). In post-anesthesia care unit, the pain score and the number of patients receiving analgesics were not different (P = 0.064 and P = 0.773). However, the duration of post-anesthesia care unit stay was significantly lower in the deep NMB group compared with in the moderate NMB group (P = 0.011). Conclusions: Deep NMB did not reduce the remifentanil requirement compared with moderate NMB in the elderly patients undergoing laparoscopic gastrectomy under SPI-guided anesthesia. Clinical trial information: NCT04205097.