Background: Spinal anesthesia with bupivacaine is administered routinely for lower limb surgeries along with additives for better hemodynamics, prolonged sensory and motor blockade. Most commonly used additives being opiods. In the present study non-opiod like dexmedetomidine is compared with buprenorphine as an adjuvant for bupivacaine in patients undergoing femur interlocking nailing surgeries. Materials and Methods: In the present randomized controlled prospective double-blinded study a total of 90 patients from either gender, aged 20–60 years of ASA I and II undergoing femur interlocking nailing surgeries under spinal anesthesia were included. The patients were randomly divided into two groups (n = 45 each) by closed envelope technique. Patients in Group B received 15 mg of 0.5% hyperbaric bupivacaine with 45 μg of buprenorphine, and Group D received 15 mg of 0.5% hyperbaric bupivacaine with 5 μg dexmedetomidine for spinal anesthesia. The duration of motor and sensory blockade, time to first analgesic requirement and any adverse events were recorded. Data were analyzed using Fisher’s exact test or Chi-square test for categorical data and analysis of variance for continuous data. The value of p < 0.05 was considered statistically significant. Results: In our study the subjects in Group D (dexmedetomidine) group had significantly longer period of motor blockade (190 ± 18.2 min) and sensory blockade (145 ± 20.2 min) compared to Group B (120 ± 17.2, 102 ± 13.5) respectively, which is statistically significant (p < 0.05 and p < 0.05* respectively). The time to first request of analgesic in the postoperative period was also longer (200 ± 21.9 min) in dexmedetomidine group when compared with Group B (130 ± 20), (p < 0.05*). There were no untoward complications (hypotension, sedation) in any groups. Conclusion: Intrathecal dexmedetomidine (5 μg) with bupivacaine for spinal anesthesia gives significantly longer duration of sensory and motor blockade than intrathecal buprenorphine (45 μg) with bupivacaine for spinal anesthesia.