Background: Erector spinae plane block (ESPB) is one modality technique, which had great outcomes among many surgeries. However, its efficacy in modified radical mastectomy remains to be fully explored. Objective: To compare between using ESPB vs traditional intravenous analgesia for control pain after breast surgeries. Patients and methods: 40 cases were included splitted into two groups. Group A included 20 cases who received ultra-sonography guided erector spinae plane block. Group B included 20 cases who had only postoperative morphine. We compared between the two groups regarding pain scores by numerical rating scale, stress response, overall fentanyl consumption, morphine consumption, intraoperative changes among mean arterial blood pressure, heart rate as well as presence of postoperative complications. Results: A statistically significant decrease in pain scores among group A was found compared to group B at all intervals (P<0.05). Also, we found statistically significant decrease among postoperative morphine consumption (P=0.001), decrease in intraoperative fentanyl needs (P<0.001), decrease in serum cortisol level 1 hour after operation (P<0.001), decrease in postoperative nausea and vomiting among group A compared to group B. While, we found non-significant change in intraoperative fentanyl consumption and in pain scores at other time intervals. Conclusion: Our study showed that erector spine plane block had a more impressive analgesic effect than intravenous analgesia in modified radical mastectomy with lower morphine consumption and lower postoperative cortisol level.