Background: Brachial plexus block is frequently used for ambulatory upper limb surgery. It can significantly reduce pain and nausea, allowing for faster discharge from hospital when compared with general anesthesia (GA). Doing this block through ultrasound has higher index of safety, allowing providers to identify the appropriate point of injection and performing this block with greater accuracy under direct visualization. Objective: the aim of the study was to compare the efficacy of bupivacaine plus dexamethasone versus bupivacaine plus dexmedetomidine as adjuvants on block characteristics including onset and duration of sensory and motor blockade, duration of postoperative analgesia, post-operative pain score and sedation score. Patients and Methods: This prospective double – blinded, randomized controlled trial included a total of 60 patients divided to two groups, each group contained 30 patients. Group 1 (dexmedetomidine group) had received 1μg/kg of dexmedetomidine + 20 ml bupivacaine 5%. Group 2 (dexamethasone group) had received dexamethasone + 20 ml of bupivacaine5%. Results: In this study the onset and duration of sensory and motor blockade was statistically shorter in dexamethasone group when compared to dexmedetomidine group. Conclusion: It could be concluded that addition of dexmedetomidine to bupivacaine prolongs the time of block and analgesia duration longer than dexamethasone, but the onset of block was shorter when dexamethasone was added to bupivacaine.