Background Regional analgesia techniques are crucial for pain management after cervical spine surgeries. Anesthesiologists strive to select the most effective and least hazardous regional analgesia technique for the cervical region. Our hypothesis is that an intermediate cervical plexus (IC) block can provide adequate postoperative analgesia compared to a cervical erector spinae (ES) block in patients undergoing anterior cervical spine surgery. Methods In this double-blind prospective trial, 58 patients were randomly assigned into two equal groups prior to the administration of general anesthesia. Patients in the IC group (n = 29) underwent ultrasound-guided bilateral intermediate cervical plexus block with 15 ml of bupivacaine 0.25% administered to each side. The ES group (n = 29) underwent ultrasound-guided bilateral cervical erector spinae plane blocks with 15 ml of 0.25% bupivacaine administered to each side at the C6 level. The primary outcome was to record the time to the first call for rescue analgesia (nalbuphine), and the secondary outcomes were to measure the performance time, the onset of the sensory block, the intraoperative fentanyl consumption, postoperative pain intensity using VAS, the postoperative total nalbuphine consumption, and postoperative complications such as nausea, vomiting, hypotension, and bradycardia. Results The performance and onset of sensory block times were significantly shorter in the IC group compared to the ES group. The time to first call for nalbuphine was significantly shorter in the IC group (7.31 ± 1.34 h) compared to the ES group (11.10 ± 1.82 h). The mean postoperative VAS scores were comparable between the two groups at the measured time points, except at 8 h, where it was significantly higher in the IC group, and at 12 h, where it was significantly higher in the ES group. The total nalbuphine consumption was significantly higher in the IC group (33.1 ± 10.13 mg) compared to the ES group (22.76 ± 8.62 mg). Conclusions For patients undergoing anterior cervical spine surgery, the intermediate cervical plexus block does not provide better postoperative regional analgesia compared to the cervical erector spinae block. Performance time and onset time were shorter in the IC group, whereas nalbuphine consumption was lower in the ES group.