Acute appendicitis is a rare complication of infectious mononucleosis (IM) and should be considered as a possible etiology of persistent abdominal pain in a patient with IM. We present a patient with IM and an incidental computed tomography diagnosis of acute appendicitis without any clinical features of appendicitis on serial abdominal examinations. Based on a review of published literature, this may be the first reported case of simultaneous presentation of IM and acute appendicitis, where no surgical intervention was performed to treat appendicitis. Appendicitis and IM appearing simultaneously lead to a high suspicion of infiltration of lymphocytes produced during IM into the appendix. Appendicitis may be monitored medically in cases of no clinical signs of acute appendicitis in patients with IM.