Acute pain after breast surgery can significantly reduce the quality of life for patients. If acute pain is not adequately treated, it can develop into chronic pain. Thoracic epidural analgesia, thoracic paravertebral block, erector spinae plane block, and serratus anterior plane block are frequently applied blocks. However, ESPB, being a fascial plane block, can yield inconsistent results regarding distribution and dermatomal area. In recent years, there has been an increase in publications applying ESPB from two levels to achieve wider distribution. As a result, this study aims to compare the analgesic efficacy of single-level (Thoracic 3) and two-level (Thoracic 2, Thoracic 4) ESPB applications.