Background:Brachial plexus block is gaining popularity day by day for upper limb surgery. The supraclavicular brachial plexus block may be used for surgical anesthesia alone or in conjunction with general anesthesia.Aims:We intended to compare the effect of dexmedetomidine and fentanyl as adjuvant to bupivacaine on onset and duration of block and postoperative analgesia during ultrasonic guided supraclavicular nerve block for upper limb surgeries.Settings and Design:This study design was a prospective randomized controlled double-blinded clinical study.Patients and Methods:Sixty patients with American Society of Anesthesiologists physical status Classes I and II, aged 18–50 years, scheduled for upper limb surgery were randomly divided into three study groups each group contains 20 patients: C Group: receive 0.5 mL/kg up to a maximum of 40 mL volume. The dose of bupivacaine was 1.5 mg/kg. D Group: Bupivacaine as control group + 1 mg/kg dexmedetomidine. F Group: Bupivacaine as control group + 1 mg/kg fentanyl. Patients were observed for onset and duration of sensory and motor blockade, duration of analgesia, postoperative pain, and adverse effects.Statistical Analysis Used:One-way ANOVA test and Chi-square test were used.Results:The onset time of sensory and motor blockade was shortened. and the duration of the block was significantly prolonged in the D Group (P < 0.001) and F Group (P < 0.001). The duration of postoperative analgesia was also longer in the D Group 13.5 h compared with the F Group 8.3 h and C Group 7.5 h. Hypotension and bradycardia were recorded in 2 patients in D Group, and nausea and vomiting were recorded in F Group.Conclusions:Addition of dexmedetomidine was better in prolongation of the duration of supraclavicular brachial plexus block and improvement of postoperative analgesia than fentanyl and bupivacaine alone without significant adverse effects in patients undergoing upper limb surgeries.