Background: Saddle block anesthesia is widely used for perianal surgeries; however, postoperative analgesia remains limited when local anesthetics are used alone. This study aimed to compare the effects of intrathecal dexmedetomidine and fentanyl as adjuvants to hyperbaric bupivacaine in saddle block for perianal surgeries Methods: This observational study in the Department of Anaesthesia, Analgesia, and Intensive Care Medicine at Bangabandhu Sheikh Mujib Medical University Hospital enrolled 64 adults (ASA I–II, 40–60 years) undergoing perianal surgery under saddle block, randomly receiving hyperbaric bupivacaine 7.5 mg with fentanyl 15 μg or dexmedetomidine 5 μg; outcomes included duration of analgesia, pain, sensory and motor block, hemodynamics, patient satisfaction, and adverse events, analyzed using SPSS v23.0. Results: Among 64 patients (mean age 45.3 ± 8.5 years; 48 males, 75%), postoperative VAS scores were lower in the dexmedetomidine group at all time points (peak 4 h: 2.75 vs 3.75). Duration of analgesia was longer with dexmedetomidine (278.5 ± 16.2 min) than fentanyl (198.7 ± 25.2 min, P = 0.0001). Motor and sensory block durations were also prolonged (162.5 vs 126.5 min and 292.1 vs 205.6 min, respectively). Hemodynamics remained stable, and adverse events were minimal (hypotension 2/32 vs 0/32; nausea/vomiting 5/32 vs 8/32; pruritus 4/32 vs 0/32). Conclusion: Dexmedetomidine as an adjuvant to hyperbaric bupivacaine in perianal surgeries under saddle block offers longer analgesia, lower pain scores, and faster sensory block onset than fentanyl.