Background and objectives: Thoracotomy is considered the most painful of surgical procedures and providing adequate analgesia is the onus for all anaesthesiologists. This study investigated the efficacy of the ultrasoundguided erector spinae plane (ESP) block in analgesia after thoracotomies. Patients and methods: Sixty patients with American Society of Anesthesiology physical status (ASA-PS) I–IV, aged more than 18years were allocated to two groups, ESP group which received the ESP block and C (control) group with no block. Single-shot U/S-guided ESP block with 20ml 0.25% bupivacaine at the 5th thoracic vertebral level was performed preoperatively in the ESP group. Postoperative 24h morphine consumption and pain scores were compared between the groups. Also, the side effects of opioid usage were compared. Main results: Postoperative morphine consumption was 22.06 ± 6.24mg in the ESP group and 30.6 ± 6.23mg in the C group (p < 0.001). Results showed that there was a significant difference between both groups in favour of the ESP group regarding visual analogue score (VAS) at rest and with coughing (p < 0.001). Conclusion: Our study findings show that US-guided ESP block exhibits a significant analgesic effect in patients undergoing thoracotomy surgery. Trial registration: ClinicalTrials.gov, NCT03749395. Registered 13 November 2018