Müllerian adenosarcoma is a distinctive type of mixed Müllerian tumor of the female genital tract. To our knowledge, no cytogenetic data have been documented on Müllerian adenosarcoma in the literature so far. We report here the chromosomal findings of a Müllerian adenosarcoma in a 15-year-old female. Cytogenetic and molecular cytogenetic analysis revealed a complex karyotype involving chromosomes 2, 8, 10, 13, 19, and 21. These numerical and structural abnormalities may be of etiologic significance. This report may highlight the potential value of molecular cytogenetic analysis in differential diagnosis of Müllerian tumors. More cases are warranted to further genetically characterize this type of neoplasm.