Background: Spinal anesthesia is a widely used regional anesthesia technique in various surgical procedures due to its effectiveness in providing profound analgesia and muscle relaxation, especially in lower abdominal, pelvic, and lower limb surgeries.The aim of this study was to evaluate the effects of intravenous ondansetron and granisetron on haemodynamic changes during spinal anaesthesia in a non-obstetric population.Materials and Methods: This was a randomized, double-blind, controlled trial conducted at a tertiary care hospital. A total of 100 patients undergoing elective non-obstetric surgeries requiring spinal anaesthesia were randomly allocated to two groups: Group O (ondansetron 4 mg) and Group G (granisetron 1 mg). Haemodynamic parameters including heart rate, mean arterial pressure (MAP), systolic, and diastolic blood pressures were recorded before and after the procedure. The primary outcomes included changes in heart rate and blood pressure, while secondary outcomes focused on the incidence of hypotension and bradycardia.Results: Both groups exhibited similar haemodynamic trends over time. Group O had a mean heart rate decrease from 72 bpm to 56 bpm, while Group G’s heart rate dropped from 70 bpm to 59 bpm. No significant differences were observed in heart rate, MAP, systolic, and diastolic blood pressures between the groups (p-values > 0.05). The incidence of hypotension was 8% in Group O and 10% in Group G, and bradycardia occurred in 5% and 4% of patients in Group O and Group G, respectively, with no statistically significant differences (p > 0.05).Conclusion: This study demonstrates that intravenous ondansetron and granisetron have comparable effects on maintaining haemodynamic stability during spinal anaesthesia. Both drugs showed similar safety profiles with no significant differences in haemodynamic parameters or the incidence of adverse events. These findings suggest that both medications can be used interchangeably in clinical practice to manage haemodynamic changes during spinal anaesthesia.