Aim: To compare the intrathecal dexmedetomedine and magnesium sulfate as adjuvants to bupivacaine in total hip replacement. Materials and Methods: This prospective, randomized, double-blinded study enrolled 90 ASA physical status I and II patients scheduled for total hip replacement surgery under spinal anaesthesia, aged 35 to 75 years, of either gender, height 159 to 189 cm, and weight 52 to 88 kg after receiving written informed consent and institutional ethical committee approval. Using computer-generated random numbers, patients were allocated into three groups: Group D received 15 mg hyperbaric bupivacaine and 0.1 ml (10 μg) DXM, Group M received 15 mg hyperbaric bupivacaine and 0.1 ml (50 mg) Mg and Group C received 15 mg hyperbaric bupivacaine and 0.1 ml normal saline as control. Results: In compared to the control group C (5.01± 1.36 and 5.36± 1.21), the start time of block, both sensory up to T10 dermatome and motor to Bromage 3 scale, was quick in the DXM group D (3.01±0.98 and 4.11±1.04) and delayed in the Mg group M (7.11± 1.36 and 7.82± 1.55). One-way ANOVA with post tests revealed statistically significant differences between the groups in both the sensory (F=94.33, P<0.001) and the motor (F=61.58, P<0.001). When compared to the control group C (204±11.47 and 157±10.11), the regression time of block, both sensory up to T10 dermatome and motor to bromage 3 scale, was delayed in the DXM group D (361±12.85 and 336±11.44) and the Mg group M (275±11.74 and 252±10.26). However, out of the three groups, the DXM group's duration was the longest. One-way ANOVA with post tests revealed statistically significant differences between the groups in both the sensory (F=59.88, P<0.001) and the motor (F=174, P<0.001). Conclusion: In contrast to intrathecal Mg, intrathecal DXM augmentation of spinal block seems to be a promising option since it causes sensory and motor block to begin and last longer while causing no appreciable hemodynamic changes. In lengthy surgical operations, ten micrograms of DXM as an adjuvant to spinal bupivacaine produces low adverse effects and offers good postoperative analgesia.