Diverticulum of the appendix is uncommon cause of right iliac fossa pain and inflammation with delayed diagnosis and high risk of complications, as it mimics acute appendicitis. Here we present a case of an elderly male patient who had lung cancer post-treatment. During the follow-up, appendicle lesion was discovered and suspected to be mucinous appendix. The pathology reported after appendectomy as appendicular diverticulosis without evidence of malignancy. As appendicular diverticulum is best confirmed by pathology, still its clinical presentation is difficult to be distinguished from other appendicular diseases. It is frequently linked to increased risk of cancer, particularly carcinoid tumors and mucinous adenomas.