Appendix vermiformis agenesis is quite rare. It is seen in 1/100,000 of patients who underwent laparotomy with an initial diagnosis of appendicitis. A 72-year-old woman who had not undergone any previous surgery was operated on for mechanical intestinal obstruction. Right hemicolectomy was performed due to obstructive tumoral mass in the hepatic flexure. There was no appendix vermiformis in exploration. Before deciding on the diagnosis of appendix agenesis, a thorough and rigorous exploration should be performed in ileocecal region and ascending colon. In our case, the diagnosis of appendix agenesis was incidental. However, it should be kept in mind that appendix agenesis may be present in patients undergoing surgery with the diagnosis of acute appendicitis.