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Introduction Both transversus abdominis plane block (TAPB) and transversalis fascia plane block (TFPB) have been shown to provide effective analgesia for caesarean section (CS) pain. However, the targeting of distinct spinal nerve branches by each technique suggests that neither approach offers complete analgesia. Moreover, the targeting of these branches by TAPB is influenced by puncture level, which has seldom been clearly defined in previous studies. This study aims to evaluate the efficacy of lower-level TAPB (L-TAPB), performed at the midpoint between the umbilicus and the anterior superior iliac spine along the anterior axillary line, by comparing it with those of classic umbilical-level TAPB (U-TAPB) and TFPB for postoperative analgesia following lower-uterine-segment (LUS) CS.Methods and analysis This single-centre, observer-blinded, randomised controlled trial will include 99 full-term parturients scheduled for elective LUS CS with a transverse incision under morphine-free spinal anaesthesia administered via a ‘needle-through-needle’ technique. Participant recruitment commenced on 3 March 2025 at the Second Affiliated Hospital of Wenzhou Medical University (WMU; Wenzhou, China). The anticipated trial completion date is October 2025. Participants will be randomised at a 1:1:1 ratio to receive L-TAPB, U-TAPB or TFPB postoperatively. Intrathecal morphine will not be used in this trial. The primary outcome of this trial will be hydromorphone consumption within the first 8 hours post-block. Secondary outcomes will include analgesic effectiveness and recovery indices such as pain scores over time, opioid consumption over time, the 15-item Quality of Recovery scale, overall satisfaction and other relevant measures. We will also assess adverse events.Ethics and dissemination All study procedures will adhere to Good Clinical Practice guidelines, with ethical approval obtained from the Ethics Committee of the Second Affiliated Hospital of WMU (approval no. 2024-K-322-02). The research findings will be published in peer-reviewed scientific journals.Trial registration number ChiCTR2500097026.