Aims: This study was designed to compare the efficacy and safety of erector spinae plane block and serratus anterior plane block in VATS (video assisted thoracoscopic surgery) patients.Methods: This prospective, single-blinded, randomized controlled trial included fifty patients aged 18 to 70 years, classified as American Society of Anesthesiologists (ASA) physical status I-III, who were scheduled to undergo elective video-assisted thoracoscopic surgery (VATS) between February 2022 and February 2023. Patients were randomly assigned to receive either an erector spinae plane block (ESPB) or a serratus anterior plane block (SAPB). In the ESPB group, a catheter was inserted at the T5 vertebral level, and 30 ml of 0.25% bupivacaine was administered. In the SAPB group, the catheter was placed into the superficial fascia overlying the serratus anterior muscle at the level of the fifth rib, and the same volume and concentration of local anesthetic was used. Postoperatively, when the Numeric Rating Scale (NRS) pain score was ≥3, a patient-controlled analgesia (PCA) device delivering 0.125% bupivacaine was connected to the catheter, and continuous infusion was initiated. Intraoperative fentanyl consumption, time to PCA connection, NRS scores, and postoperative morphine use were recorded. Data were analyzed using R version 4.0.0. Appropriate parametric or non-parametric tests were used based on data distribution. Repeated measures were evaluated with the Friedman test, and a p-value