Background: Erector spinae plane block is a locoregional anaesthetic technique widely used in several different surgeries due to its safety and efficacy. The aim of this study is to assess its utility in spinal degenerative and traumatic surgery in western countries and for patients of Caucasian ethnicity. Methods: Patients undergoing elective lower-thoracic and lumbar spinal fusion were randomised into two groups: the case group (n = 15) who received erector spinae plane block (ropivacaine 0.4% + dexamethasone 4 mg, 20 mL per side at the level of surgery) plus postoperative opioid analgesia, and the control group (n = 15) who received opioid-based analgesia. Results: The erector spinae plane block group showed significantly lower morphine consumption at 48 h postoperatively, lower need for intraoperative fentanyl (203.3 ± 121.7 micrograms vs. 322.0 ± 148.2 micrograms, p-value = 0.021), lower NRS score at 2, 6, 12, 24, and 36 h, and higher satisfaction rates of patients (8.4 ± 1.2 vs. 6.0 ± 1.05, p-value < 0.0001). No differences in the duration of the hospitalisation were observed. No erector spinae plane block-related complications were observed. Conclusions: Erector spinae plane block is a safe and efficient opioid-sparing technique for postoperative pain control after spinal fusion surgery. This study recommends its implementation in everyday practice and incorporation as a part of multimodal analgesia protocols. Trial registration: The study was approved by the local ethical committee of Romagna (CEROM) and registered on ClinicalTrials.gov (NCT04729049). It also adheres to the principles outlined in the Declaration of Helsinki and the CONSORT 2010 guidelines.