Objective To investigate the sedative, analgesic and hemodynamic effects of intranasal dexmedetomidine (Dex) on ultrasound‑guided brachial plexus block during the upper limb surgery in adults. Methods Sixty patients, scheduled for elective upper limb surgery under ultrasound‑guided brachial plexus block were recruited and equally divided into intranasal Dex group (group D) and control group (group C) using a random number table method, 30 cases in each group. Patients in group D received intranasal Dex of 1 μg/kg (100 mg/L) via a mucosal atomization device (MAD) 30 min before anesthesia, while patients in group C received volume‑matched intranasal normal saline over the same period. All patients then underwent ultrasound‑guided interscalene brachial plexus block with a 20 ml mixture of 0.33% ropivacaine and 1% lidocaine. Measurements included mean arterial pressure (MAP), heart rate, pulse oxygen saturation (SpO2) and Ramsay Sedation Scale scores at the time of entering room (T0), before plexus block (T1), during plexus block (T2), after plexus block (T3), skin incision (T4), and 20 min after the start of surgery (T5). The Visual Analogue Scale (VAS) scores of pain at T2 and T4 were observed. The use of fentanyl during the operation and the adverse reactions such as bradycardia, hypotension, nausea, vomiting and respiratory depression were recorded. The satisfaction scores of patients about anesthesia after surgery were also recorded. Results There is no significant differences in SpO2 at all time points between two groups (P>0.05). At the time of T0, no significant differences were found in MAP, heart rate, Ramsay Sedation Scale scores between two groups (P>0.05). Compared with T0, patients in group D had lower MAP, lower heart rate and higher Ramsay Sedation Scale scores at the time of T1‒T5 (all P<0.05), while there were no significant differences in group C (P>0.05). Compared with group C, patients in group D showed lower MAP, lower heart rate and higher Ramsay Sedation Scale scores at the time of T1‒T5 (all P<0.05). The VAS scores of pain at T2 and T4 and the total amount of fentanyl during the operation were significantly lower in group D (P<0.05). There were no significant differences in the incidence of adverse events such as hypotension, bradycardia, nausea and vomiting between the two groups (P>0.05). The satisfaction scores of patients about anesthesia in group D were also significantly higher than group C (P<0.05). Conclusions For patients undergoing upper limb surgery, intranasal Dex of 1 μg/kg via a MAD 30 min before ultrasound‑guided brachial plexus block could provide excellent sedation and analgesia, stabilize hemodynamics, decrease the consumption of analgesics, and improve the patient's level of comfort, without inducing any adverse effects.