Background The administration of adequate analgesia post-operatively has been associated with fewer cardiopulmonary complications, lower morbidity and mortality, lower healthcare costs, and higher patient satisfaction. One of the most effective ways to raise the standard of healthcare would be standardization of multimodal analgesia with enhanced recovery after surgery. Adjuncts to spinal anesthetists can achieve a better post-operative pain relief with less doses of rescue analgesia. Methods This was a prospective, randomized trial conducted on 60 women undergoing abdominal hysterectomy under spinal anesthesia. We evaluated the impact of adding 0.5 mL (2.5 mg) of intrathecal midazolam versus 25 mcg of intrathecal fentanyl (0.5 mL) with 2.5 mL injection of 0.5% bupivacaine (hyperbaric) (12.5 mg). The outcomes were prolongation of analgesia in the post-operative period, onset and duration of sensory and motor blockade, stable hemodynamics, and any adverse reactions to the study drugs. Results The two groups, group M (midazolam + hyperbaric bupivacaine) and group F (fentanyl + hyperbaric bupivacaine), had similar distribution for age, weight, and type and duration of surgical procedure. Both groups had stable vital parameters and experienced a similar onset of sensory and motor blockade. Intraoperative modified Ramsay sedation score was better in group M in comparison to group F. However, mean of elapsed time of two-segment regression of sensory block, from T12 to L1 level, and mean time to regression, from Bromage score 3 to 2, were longer in group F. Group F also had a better visual analogue scale (VAS) score in the post-operative period than group M, and group F experienced a longer average post-operative analgesic duration (lasting for 367.73 minutes) as compared to group M (lasting for 254.9 minutes), having a difference that was of statistical significance (p < 0.001). No substantial adverse reactions were seen in either group. Conclusion The duration of post-operative analgesia is significantly prolonged when 25 mcg of adjuvant intrathecal fentanyl is used with 0.5% bupivacaine (hyperbaric) as compared to intrathecal midazolam 0.5 mL (2.5 mg) in women undergoing abdominal hysterectomy under spinal anesthesia. Both fentanyl and midazolam have minimal adverse reactions and are safe to use as adjuvants to 0.5% of bupivacaine (hyperbaric) in surgeries conducted in the lower abdomen.