Background: In our study, we investigated the effect of adding neostigmine to local anesthetic on the supraclavicular brachial plexus block. Patients and Methods: This prospective, randomized, blinded controlled experiment included 80 patients of either sex with an ASA I or II physical status who were planned for forearm operations under ultrasound-assisted supraclavicular brachial plexus block. Participants were separated randomly into two groups and given a supraclavicular block with 25 mL of 0.5% bupivacaine and 1 mL of 0.9 % saline for the control group and 25 mL of 0.5% bupivacaine and 1 mL of neostigmine (0.5mg) for the neostigmine group. Results: In the neostigmine group, sensory and motor blockade began earlier and lasted longer than in the control group. The neostigmine group took substantially longer to seek their first analgesia. The neostigmine group used fewer analgesics in total. At 1, 2, 4, and 6 hours, the neostigmine group had statistically reduced VAS scores than the control group. Conclusion: Patients undergoing forearm procedures benefit from the usage of neostigmine in addition to bupivacaine in ultrasound-assisted supraclavicular brachial plexus block because it reduces the onset of sensory and motor block and lengthens its duration. These results were clear with a dosage of (0.5 mg).