The occurrence of synchronous tumors is rare and there have been only a few reported cases. In this particular report, a 30-year-old female presented with abnormal heaviness and anorexia for one month. The case involved the presence of two simultaneous tumors: an immature teratoma in the ovary and a carcinoid tumor in the appendix. This case was complex and presented challenges for diagnosis and treatment. Although synchronous tumors are uncommon, they should be considered as a possibility in the differential diagnosis. Physicians may encounter difficulties in both clinical and histopathological diagnosis when dealing with such cases.