Background: Administration of adjuvant drugs epidurally in combination with local anesthetics offers new dimensions in the management of postoperative pain. This study aimed to compare the addition of either nalbuphine or dexmedetomidine to epidural bupivacaine for postoperative analgesia in lower limb orthopedic surgeries under combined spinal-epidural anesthesia. Methods: This prospective randomized double-blind study included 69 patients scheduled for lower limb orthopedic surgeries. Anesthesia was started with 15 mg hyperbaric bupivacaine 0.5% intrathecally, and then an epidural bolus dose of 12 ml (10 ml 0.25% bupivacaine with 2 ml normal saline in group C, 2 ml (10 mg) nalbuphine in group N or dexmedetomidine 2 ml (100 µg) in group D was administered when sensory regression to T10. Postoperatively, when visual analogue scale (VAS) was ≥ 3, an epidural top-up dose of 8 ml (6 ml 0.25% bupivacaine plus 2 ml normal saline in group C, 2 ml (2 mg) nalbuphine in group N or 20 µg dexmedetomidine (2 ml) in group D was given. The primary outcome was to evaluate the duration of postoperative analgesia and secondary outcomes were any side effects and patient satisfaction. Results: The onset of epidural analgesia was 17.83 ± 2.53 versus 13.39 ± 1.27 versus 12.17 ± 1.27 min in groups C, N and D, respectively (p value < 0.001). The mean duration of analgesia was 241.3 ± 14.24 versus 318.38 ± 22.54 versus 365.87 ± 18.01 min in groups C, N and D, respectively (p value < 0.001). The mean sedation score was less in group C than group N and D (P < 0.001). The patient satisfaction score showed the lowest degree of satisfaction in group C (p value < 0.001). Top-up doses consumed and total analgesic requirements were lower in groups N and D than in group C. There was a statistically significant difference between the studied groups regarding VAS over time (p value < 0.001), intraoperative bradycardia (p value 0.029), and shivering (p value 0.029). Conclusion: The addition of either nalbuphine or dexmedetomidine to epidural bupivacaine was effective for postoperative analgesia in terms of onset, duration, and patient satisfaction with the superiority of dexmedetomidine over nalbuphine.