Background: Peripheral nerve blocks are widely used for upper extremity orthopedic surgeries because they provide excellent surgical anesthesia and postoperative analgesia while reducing systemic opioid requirements. Adjuvants such as dexamethasone and fentanyl have been used with local anesthetics to prolong the duration of analgesia and improve block characteristics. This study aimed to compare the efficacy of perineural dexamethasone versus fentanyl as adjuvants to 0.5% bupivacaine in ultrasound-guided infraclavicular brachial plexus blocks for forearm orthopedic surgeries. Aim: We conducted this study to determine the comparative effects of adding either dexamethasone or fentanyl as an adjuvant to bupivacaine 0.5% (25ml) for ultrasound-guided infraclavicular brachial plexus block for forearm orthopedic surgeries. Our analysis focused on the block characteristics including onset and duration of sensory and motor blockade, as well as time to first rescue analgesia and postoperative pain scores, were assessed. Methods: A Randomised, double blind, comparative study consisting of 60 patients fulfilling inclusion criteria were randomised into two groups of 30 each and included in the study. Group A received 25 mL of 0.5% bupivacaine with 8 mg dexamethasone. Group B received 25 mL of 0.5% bupivacaine with 50 mcg fentanyl. Statistical methods used: Chi-Square test, Fisher exact test. NPO confirmed. Written informed consent obtained. Standard monitors connected. The block was administered using a portable ultrasound machine equipped with a linear transducer (Sonosite™ 8-13MHz). With the patient in a supine position and their head turned to the contralateral side and hand abducted to 90 degree. Strict aseptic precautions was observed. The brachial plexus was identified in the infraclavicular fossa using a parasagittal plane transducer placement. On ultrasound, the plexus typically appears as a hypoechoic circles encircled by a hyperechoic ring. A 23G needle (Stimuplex Ultra, B. Braun Melsungen AG) was employed for precise needle localization. Results: Demographic characteristics were comparable between the groups. The fentanyl group demonstrated a significantly faster onset of sensory block (6.85 ± 1.52 min vs. 7.95 ± 1.41 min, p=0.012) and motor block (5.25 ± 1.10 min vs. 6.50 ± 1.15 min, p<0.001). However, the dexamethasone group showed significantly prolonged sensory block duration (19.50 ± 1.85 h vs. 12.80 ± 1.60 h, p<0.001), motor block duration (19.25 ± 1.80 h vs. 12.10 ± 1.75 h, p<0.001), and postoperative analgesia. The mean time to first rescue analgesia was significantly longer in the dexamethasone group (22.12 ± 1.82 h vs. 12.70 ± 1.55 h, p<0.001). Postoperative pain scores were comparable between the groups (p=0.825). Conclusion: Perineural dexamethasone and fentanyl both enhanced the efficacy of ultrasound-guided infraclavicular brachial plexus block when used as adjuvants to bupivacaine. Fentanyl provided a faster onset of sensory and motor blockade, whereas dexamethasone significantly prolonged the duration of sensory and motor block and extended postoperative analgesia. Therefore, dexamethasone appears to be a superior adjuvant for prolonged postoperative pain control in forearm orthopedic surgeries performed under infraclavicular brachial plexus block.