To date, there have been no reports on the long-term effects of a method that combines external hemorrhoidectomy with aluminum potassium sulfate and tannic acid (ALTA) sclerotherapy. This study aimed to investigate the efficacy and safety of external hemorrhoidectomy combined with ALTA sclerotherapy (EA) in reducing postoperative complications associated with conventional hemorrhoidectomy. EA was performed under sacral epidural anesthesia, and ALTA sclerotherapy was applied to the remaining internal hemorrhoids after resection of the external hemorrhoids. Mixed internal and external hemorrhoids were treated with EA, whereas internal hemorrhoids without external hemorrhoids were treated with ALTA sclerotherapy. The three EA patterns were defined as EA1, EA2, and EA3, depending on the number of EAs performed. This study included 3,403 patients who underwent EA for grade II-IV mixed hemorrhoids. EA1 was the most common, with 1,789 (52.6%) cases, followed by EA2 (36.2%) and EA3 (11.2%). Postoperative complications occurred in 120 (3.5%) patients and increased with the number of EAs, with fever and bleeding being common in the early postoperative period, and perianal abscess and/or fistula being common after 1 month. The mean postoperative follow-up period was 26.4 months, and 136 (4.0%) patients underwent reoperation for recurrent internal or mixed hemorrhoids. The reoperation rate for EA1 was significantly higher than that for EA2 and EA3. The 5- and 10-year cumulative recurrence-free rates were 92.5% and 67.2%, respectively. EA is as curative as conventional hemorrhoidectomy and reduces postoperative complications. Therefore, EA is the preferred procedure for patients with mixed hemorrhoids.