Background: Brachial plexus block is a crucial technique in regional anesthesia for upper limb surgeries. The choice of local anesthetic and adjuncts impacts the quality and duration of the block. This study explores the extension of brachial plexus block using 1.5% Lidocaine and compares it with 1.5% Lidocaine-Adrenaline-Buprenorphine combination. Methods: Fifty patients undergoing elective upper limb surgery were randomly assigned to Group A (1.5% Lidocaine-Adrenaline) and Group B (Lidocaine-Adrenaline-Buprenorphine). Onset and duration of sensory and motor block, hemodynamic parameters, and adverse effects were recorded. Results: Group B exhibited a significantly longer duration of analgesia compared to Group A (p < 0.001), while the onset of block was similar. There were no significant differences in the degree of sensory block between the two groups, but patients in Group B experienced increased drowsiness (p < 0.001). Complications and the need for general anesthesia supplementation were comparable between the groups. Conclusion: Lidocaine-Adrenaline-Buprenorphine extends the duration of brachial plexus block with a similar onset compared to Lidocaine-Adrenaline. However, it is associated with increased drowsiness. This study highlights the clinical significance of Buprenorphine as an adjunct in upper limb regional anesthesia, offering prolonged analgesia with potential considerations for patient alertness during surgery.