Background: Effective pain management after caesarean delivery is essential to promote maternal recovery, facilitate early mobility, and support mother-infant bonding. Traditionally, intrathecal morphine (ITM) has been widely used due to its strong analgesic effects, but concerns about opioid-related side effects have led to growing interest in alternative regional techniques such as the quadratus lumborum block (QLB). Comparative evidence on the efficacy of these approaches in obstetric patients remains limited. Methods: In a randomized trial, 70 cesarean patients underwent spinal anesthetic at Assiut University Hospital. The study compared bilateral posterior QLB with 0.25 % bupivacaine to 100 μg ITM. Secondary outcomes included pain scores, time to first morphine request, side effects, quality of recovery, and functional outcomes; the primary outcome was 24-hour IV morphine consumption. Results: Morphine consumption over 24 h was similar between the ITM and QLB groups, averaging 6.4 mg and 8.5 mg, respectively. Pain levels at rest and during movement did not differ significantly between the two groups at any time point. However, a subgroup analysis showed that QLB patients with a BMI of 30 kg/m² or higher required more morphine and reported higher peak pain scores compared to those in the ITM group (10.5 mg vs 7.4 mg, p < 0.05). No such difference was seen in patients with a BMI below 30 kg/m². In a multivariate analysis, BMI emerged as the only significant predictor of 24-hour morphine consumption (p = 0.016). Conclusion: ITM and posterior QLB provide comparable postoperative analgesia after cesarean delivery for the general population. However, patient factors such as BMI and age may influence postoperative opioid requirements and should be considered when selecting an analgesic technique to optimize recovery and minimize side effects.