Background: The supraclavicular brachial plexus block (SBPB) is a widely used approach in regional anesthesia (RA). The use of ultrasound (USG) guidance significantly reduces the complications of SBPB. Recent advancements suggest that combining lower concentrations of levobupivacaine with dexmedetomidine can maintain efficacy while minimizing adverse reactions. Levobupivacaine 0.5 and 0.25% have been used in combination with dexmedetomidine at doses of 1 µg/kg of body weight; however, the effects of concentrations of levobupivacaine (0.375 and 0.25%) on block parameters and hemodynamics in SBPB, when combined with a fixed dose of dexmedetomidine, for upper limb procedures, remain underexplored. This study investigates the efficacy of 0.375 and 0.25% levobupivacaine, combined with a fixed dose of dexmedetomidine, in USG-guided SBPB. Materials and methods: A prospective, randomized, double-blind trial was conducted on a total of 60 patients scheduled for elective upper limb surgery from June 2021 to May 2022 at our regional medical center. Participants were divided into two groups of 30 each. Group I received 30 mL of 0.375% levobupivacaine with 1 µg/kg dexmedetomidine, and group II received 30 mL of 0.25% levobupivacaine with 1 µg/kg dexmedetomidine. The duration of analgesia was the primary outcome. The onset and duration of sensorimotor blockade, hemodynamic variables, sedation score, and adverse effects were secondary outcomes. Statistical analysis was performed using appropriate tests in Excel for Windows ver. 15, 2013, United States of America. Results: Group I exhibited a significantly faster onset of sensory block (3.93 ± 1.70 minutes) compared to group II (6.07 ± 1.53 minutes). Additionally, group I patients experienced earlier paresthesia and paralysis of the hand and shoulder joints. The duration of analgesia was significantly longer in group I (p < 0.05). Hemodynamic evaluation 2 hours postblock showed no significant differences in mean blood pressure or heart rate between the groups (p > 0.05). Sedation scores, measured using the modified Ramsay Sedation Scale, were comparable between the groups (p > 0.05), with average scores of 2.27 ± 0.45 for group I and 2.23 ± 0.43 for group II. Conclusion: Both concentrations of levobupivacaine, when combined with dexmedetomidine, provided effective surgical anesthesia. However, 0.375% levobupivacaine resulted in a faster onset and prolonged sensory and motor blockade duration compared to 0.25% levobupivacaine. Neither combination resulted in significant side effects or complications, highlighting their safety and efficacy for SBPB.