Background: Magnesium sulfate is one of the common adjuvants to general anesthetics. Limited number of clinical studies has been done to evaluate the Effect of adding magnesium sulfate to general anesthesia on Neutrophil to lymphocyte Ratio (NLR). Therefore, this study assessed these effects in patients undergoing lower abdominal surgery. Objectives: This study mainly aims to evaluate the Effect of adding magnesium sulfate to general anesthetics on NLR and its relation to postoperative pain assessment using the VAS score. Patients and methods: The prospective randomized controlled, double-blind clinical trial involved 60 female patients (age 40-60 years) of American Society of Anesthesiologists (ASA) physical status I- II who were scheduled for elective lower abdominal hysterectomy under general anesthesia and divided into two groups 30 patients in each group (group S and group M). In group (M), magnesium sulfate 50 mg/kg in normal saline with a total volume of 100 ml as loading over 20 minutes given before induction of anesthesia followed by 10 mg/ kg/ hour till the end of the surgery, in group (S) 100 ml of 0.9% NaCl as loading over 20 minutes given before induction of anesthesia followed by 0.1 ml/kg/hour till the end of surgery. Blood samples were withdrawn for NLR calculation, and postoperative pain assessment was done using VAS Score. Results: There was a statistically significant decrease in postoperative NLR in group (M) compared to group (S) at 4 and 8 h. with p-value =0.001. As regards pain assessment using VAS, there was a statistically significant decrease in group (M) compared to group (S) at baseline and 4 h. postoperatively with P value-0.001. Conclusion: Intravenous magnesium sulfate administered preoperatively in female patients over 40 years old undergoing lower abdominal hysterectomy at dosages of 50 mg/kg decreased postoperative N/L ratio and decreased postoperative pain.