PURPOSE: Recently, single incision laparoscopic surgery (SILS) has been studied for its being less invasive surgery and having cosmetic improvement. We investigated the application of SILS for an appendectomy (SILS-A) in cases of complicated appendicitis and compare it with a conventional laparoscopic appendectomy (C-LA). METHODS: This study involved a total of 40 patients who underwent C-LA or SILS-A in patients with complicated appendicitis; 25 patients received a C-LA, and the other 15 patients received a SILS-A. The clinical outcomes and cosmetic results were compared between the groups. RESULTS: The SILS-A procedures were performed successfully in patients with complicated appendicitis, but 6 patients who underwent SILS-A needed an additional port for dissection and drainage. Clinical outcomes and postoperative complications were similar in both study groups. The SILS-A group showed significantly higher numbers of pain control than the C-LA group, and the one port SLLS-A group showed significantly better cosmetic result than the C-LA group. CONCLUSION: SILS-A is technically feasible and safe in patients with complicated appendicitis. However, SILS-A has more postoperative pain than C-LA, and more active pain control should be considered for patients undergoing SILS-A.