Background and Aims: Pain after modified radical mastectomy (MRM) has been successfully managed with thoracic paravertebral block (TPVB). The purpose of this study was to evaluate the effect of adding dexamethasone or ketamine as adjuncts to bupivacaine in TPVB on the quality of postoperative analgesia in participants undergoing MRM. Methods: This prospective randomised controlled study enrolled ninety adult females scheduled for MRM. Patients were randomised into three groups (30 each) to receive ultrasound-guided TPVB before induction of general anaesthesia. Group B received bupivacaine 0.5% + 1 ml normal saline, Group D received bupivacaine 0.5% + 1 ml dexamethasone (4 mg) and Group K received bupivacaine 0.5% + 1 ml ketamine (50 mg). Patients were observed for 24 h postoperatively to record time to first analgesic demand as a primary outcome, pain scores, total rescue morphine consumption and incidence of complications. Results: Group K had significantly longer time to first analgesic demand than group D and control group (18.0 ± 6.0, 10.3 ± 4.5 and 5.3 ± 3.1 hours respectively; P = 0.0001). VAS scores were significantly lower in group D and group K compared to control group at 6h and 12 h postoperative (p 0.0001 and 0.0001 respectively) while group K had lower VAS at 18 hours compared to other two groups (P = 0.0001). Control group showed the highest mean 24 h opioid consumption (8.9 ± 7.9 mg) compared to group D and group K (3.60 ± 6.92 and 2.63 ± 5.24 mg, P = 0.008,0.001 respectively). No serious adverse events were observed. Conclusion: Ketamine 50 mg or dexamethasone 4 mg added to bupivacaine 0.5% in TPVB for MRM prolonged the time to first analgesic request with no serious side effects.