Background <p>The pericapsular nerve group (PENG) block is increasingly used for analgesia in hip-related procedures. However, the optimal local anesthetic volume remains unclear. This randomized non-inferiority trial aimed to compare the analgesic efficacy of 10 mL versus 20 mL PENG block after total hip arthroplasty, hypothesizing that the lower volume would provide non-inferior analgesia.</p> Methods <p>In this single-center randomized controlled non-inferiority trial, 50 patients undergoing hip replacement surgery received an ultrasound-guided PENG block with 0.25% bupivacaine, either 20 mL (<i>n</i> = 25) or 10 mL (<i>n</i> = 25). Postoperative analgesia was provided using morphine patient-controlled analgesia. Pain scores at rest and during movement were assessed at predefined time points up to 24&#xa0;h postoperatively. The primary outcome was the NRS pain score at rest 1&#xa0;h after surgery. Secondary outcomes included opioid consumption, quadriceps muscle strength, postoperative nausea and vomiting, and patient satisfaction.</p> Results <p>There were no significant differences between groups in opioid-related side effects, quadriceps muscle weakness, patient satisfaction, or length of hospital stay. Non-inferiority analysis demonstrated that the median differences in NRS scores between groups remained within the predefined non-inferiority margin of 1 NRS point at all assessment time points. Non-inferiority of the 10 mL PENG block was confirmed for the primary outcome.</p> Conclusions <p>A 10 mL PENG block provides postoperative analgesia non-inferior to a 20 mL volume without increasing opioid consumption or motor weakness, suggesting that lower volumes may be sufficient and potentially safer after total hip arthroplasty.</p> Trial registration <p>ClinicalTrials.gov, NCT06166602. Registered on December 04, 2023. Retrospectively registered (study start date July 30, 2023).</p>