Background Spinal anesthesia (SA) is the method of choice for surgery below umbilicus like elective cesarean section. However, Spinal anesthesia is associated with hypotension and limited analgesia duration. To minimize those complications adding opioids like fentanyl either sequentially with separate syringe or pre mixed with local anesthetics become common practice. Objective To compare the hemodynamic and analgesic effect of sequential versus pre mixed injection of intrathecal fentanyl with hyperbaric bupivacaine for patients who underwent elective CS under Spinal anesthesia. Method A prospective cohort study was performed on parturient who undergone elective cesarean section from 01 January 2020 to 30 March 2020. The decision to give either sequential or premixed drug was based on the responsible anesthetists. Sixty-six American society of Anesthesiologist Ⅱ age ≥18 was recruited. Those who received sequentially were grouped as (S- group) and those who had received pre mixed technique were grouped as (M-group). Data were entered into Epi Info version 7.0 and transported into SPSS Version 22 for analysis. Based on normality assumption, analysis was done by independent t -test for normally distributed data. Whereas Mann –Whitney U test for non-normally distributed data and x2 (Chi-square) test for categorical variable. P-value <0.05 was considered as statistically significant. Result Significant reduction in intra operative mean arterial blood pressure was seen in premixed group compared to Sequential group until 15th minute immediately after spinal anesthesia. Thus, the incidence of hypotension was higher in M − group compared to S- group, (p < 0.05). The median Postoperative pain VAS score was significantly lower in the S - group compared to M − group of 4th, 5th and 6th hr. The mean time for 1st rescue analgesic request time was prolonged in the S - group compared to M − group (287.909 ± 15.255 vs. 261.39 ± 25.378) min respectively (p < 0.001). Conclusion The Sequential intrathecal injection of fentanyl and hyperbaric bupivacaine provided significant improvement in the blood pressure stability and of sensory and motor block compared to premixed groups.