Appendicitis is a common diagnosis encountered by the acute care surgeon. Management of complicated appendicitis is controversial and often involves initial nonoperative therapy with interval appendectomy. This study reviews single-institutional experience with management of complicated appendicitis with interval appendectomy and addresses an unusually high occurrence of incidental appendiceal malignancies observed with a review of relevant literature. A retrospective review of all diagnoses of appendicitis was performed over 5 years at a tertiary care center. Patient demographics, time to surgery, operative technique, pathologic diagnosis, and clinical outcomes were examined. Three hundred fifteen patients were diagnosed with acute appendicitis. Of these, 24 (7.6%) were deemed complicated and did not undergo immediate appendectomy, and 18 ultimately underwent appendectomy at our institution and were included in analysis. There were no statistical demographic or symptomatic differences between the immediate and interval appendectomy patients. Ninety-nine per cent of the immediate appendectomy patients were treated laparoscopically; 78 per cent of the interval group underwent attempted laparoscopic treatment with 56 per cent completed without conversion to open (P < 0.01). Neoplasms were discovered in 1 per cent of the acute appendectomy group and 28 per cent of the interval appendectomy group (P < 0.0001). Two of the three neoplasms in the acute group were carcinoid, whereas three of the five neoplasms in the interval group were adenocarcinoma. Surgeons should consider appendiceal or colonic neoplasms in cases of complicated appendicitis when nonoperative management is considered. This is most important in patients older than 40 years, in those who forego interval appendectomy, or in those who could be lost to follow-up.