Shoulder arthroscopic surgery is associated with moderate to severe postoperative pain, which may hinder early mobilization and functional recovery. Interscalene block (ISB) is commonly used to provide effective analgesia but is frequently associated with hemidiaphragmatic paralysis due to phrenic nerve involvement. Cervical erector spinae plane block (ESPB) has been proposed as an alternative regional technique that may provide analgesia while reducing respiratory-related adverse effects. This randomized controlled trial aims to compare the analgesic efficacy and safety of cervical ESPB versus continuous ISB in patients undergoing shoulder arthroscopic surgery.