A 54-year-old male presented to the clinic, complaining of dull lower abdominal pain that started a day ago. There was a tenderness on right lower quadrant on palpation and abdominal computed tomography(CT)showed that dilated appendix with a diameter of 12 mm. The patient was diagnosed with acute appendicitis and laparoscopic appendectomy was performed on the same day. The tip of the appendix was swollen and looked purple, gangrenous appendicitis findings were identified. However, histopathology detected GCA on resected appendix with positive surgical margin and additional tumor resection was indicated. Laparoscopic ileocecal resection with D3 lymph nodes dissection was performed 24 days after the first surgery. Resected specimen showed that the stump of the appendix was palpable as a mass in the orifice of the appendix and histopathology revealed the remnant of the appendiceal GCA. No lymph nodes tumor metastasis was identified. Chromogranin A and synaptophysin were positive and Ki-67 was approximately 50%. According to the guideline of neoadjuvant chemotherapy for colon cancer, oral 5-fluorouracil therapy was performed for half a year after the second surgery and the patient remains still healthy without recurrence 1 year after the surgery. Here, we experienced a rare case of GCA of the appendix that was detected incidentally after appendectomy for acute appendicitis.