Dissecting gonadoblastoma (DGB) of the ovary, a recently described terminology, defines a unique distribution of neoplastic germ cells. Here, we report a case of incidental DGB coexistent with an atypical endometriotic cyst occurring in a 23-year-old woman. The ovarian cyst was lined by endometrial-like glands and stroma. Some glands displayed nuclear enlargement and hyperchromasia, and abundant eosinophilic cytoplasm with occasional intracytoplasmic hemosiderin and mucin vacuoles. The neoplastic germ cells resembled those of ovarian dysgerminoma and were diffusely distributed within the ovarian stroma, which was stretched around the wall of the endometriotic cyst. These cells were arranged in nests and cords, possessing clear cytoplasm and centrally located round nuclei with prominent nucleoli and occasional mitoses. Chromosomal analysis revealed a 46,XX karyotype. We describe the clinical, histological, immunophenotypical, and genetic features of ovarian DGB incidentally detected in the ovarian cystectomy specimen of a woman with normal female karyotype.