Spinal anaesthesia with or without any adjuvant is the most commonly performed anaesthesia for almost all lower limb orthopaedic surgeries. Present study is aimed to compare analgesic efficacy between intrathecal fentanyl and intrathecal dexmedetomidine as an adjuvant to bupivacaine for unilateral lower limb orthopaedic surgeries. Ninety patients aged 18 to 60 years scheduled for lower limb open orthopaedic surgery were randomly allocated in two groups to receive the drugs intrathecally either fentanyl 25 μg or dexmedetomidine 5 μg. Pain was measured by VAS scores postoperatively at arrival in PACU and at intervals, for first 12 hours. At any time, if the score was ≥ 4, rescue analgesia was given in the form of Inj. Diclofenac 75 mg intravenously. Chi-square test was used for qualitative variables where as unpaired 't' test was used for quantitative variables. Mann-Whitney U test was used to compare the significance between VAS score . There was no significant differences with respect to mean age, sex distribution, mean weight and ASAdistribution between two groups. Mean duration of sensory and motor block was significantly higher in Group dexmedetomidine as compared to Group fentanyl. Mean quantity of post operative rescue analgesia requirement was significantly less in Group dexmedetomidine as compared to Group fentanyl. Group dexmedetomidine has lower median VAS score. Intrathecal dexmedetomidine as an adjuvant to bupivacaine is useful in enhancing postoperative analgesia and also reduces requirement of total rescue analgesia.