Ovarian teratomas are the most common germ cell tumour and they contain tissue of ectodermal, mesodermal and endodermal origin. Ovarian teratomas are classified into mature cystic teratomas, immature teratomas and monodermal teratomas. Acute appendicitis is a frequent surgical emergency whose diagnosis can be made clinically. For a female of reproductive age, gynaecological causes need to be considered as a differential diagnosis. Further investigations, including imaging, should be arranged in doubt. A thorough history, examination and appropriate investigations will help to prevent unnecessary surgical interventions.