Objective: To compare between the results Milligan-Morgan’s operation using the Harmonic Scalpel (HSH) and diathermy (DH) in the surgical treatment of grade III and IV hemorrhoids. Methods: The comparative study was conducted at Kafr El Sheikh University Hospital, Egypt, from December 2018 to December 2019, 40 patients presented with grade III and IV hemorrhoids were enrolled in the study and were divided into 2 groups; DH group (20 patients) and HSH group (20 patients). Results: The mean age of patients who underwent DH was 39.8 ± 11.34 years and 42.8±10.67 years in HSH group. The mean operative time of the DH and HSH groups was 18.95 ± 6.85 minutes and 14.75 ± 4.93 minutes, respectively (p<0.001). There was statistically significant difference between both groups regarding postoperative pain and amount of analgesia used. On day of the surgery, postoperative pain ranged from 4.5 to 6 with a median of 5 according to VAS score in HSH group compared to 6.5 to 8 with a median of 7 in DH group. Conclusion: Harmonic Scalpel is better than diathermy in terms of reduced postoperative pain, reduced doses of analgesia needed postoperatively and excellent hemostasis despite being slightly costly in terms of treating hemorrhoids. Clinical Trial Number: MKSU 50-5-18