Mature cystic ovarian teratomas are ovarian tumors that are most common in reproductive age women. MCTs are benign germ cell tumors that arise from totipotent germ cells in the ovary. Endometriosis is also a common gynecologic disease affecting reproductive age women. Endometriosis is a progressive and chronic disease associated with inflammation, chronic pelvic pain, and infertility. However, the pathophysiology, symptoms, diagnosis, and management of each disease are well known, but there is little information on the simultaneous occurrence of these two diseases. Therefore, the epidemiology, clinical symptoms, imaging, management, and the risk of malignant transformation of the coexistence of MCTs and endometriosis are discussed herein. PubMed and any reports of individuals with both MCTs and endometriosis were searched for all articles written in the English-language medical literature until May 2020. This review indicates that diagnosis and treatment of the coexistence of MCTs and endometriosis are more complicated when two diseases coexist than when only one disease exists. In conclusion, this comorbid conditions may not be as rare as it was previously thought. To understand and treat this complex condition, more studies are essential.