Forty-seven patients undergoing shoulder arthroscopy were randomized to receive either an ultrasound-guided interscalene block (ISB) with 12 mL of 0.5% ropivacaine and 50 µg of dexmedetomidine (n=24) or 12 mL of 0.5% ropivacaine alone (n=23). The primary outcome was the incidence of rebound pain. Secondary outcomes included Numeric Pain Rating Scale (NRS) scores at 6, 12, 24, and 48 hours postoperatively, time to first analgesic request, patient-controlled analgesia (PCA) sufentanil consumption, sleep disturbances, and postoperative nausea and vomiting (PONV). Outcomes were assessed over 48 hours postoperatively. Overall, the results showed that the addition of dexmedetomidine significantly reduced the incidence of rebound pain, prolonged sensory and motor block duration, delayed the first analgesic request, and lowered opioid consumption. The findings suggest that perineural dexmedetomidine is an effective adjuvant for reducing rebound pain and improving early postoperative pain management after shoulder arthroscopy.