Sex hormone-related alopecia is a rare clinical condition in dogs. A 9-year-old female dog was presented with a history of symmetrical alopecia on the caudal aspects of both thighs. A dermatophyte culture, skin scrapes, and acetate strip examinations were negative for dermatophytes, parasites, and yeasts. The only abnormality in abdominal ultrasonography was multiple cystic follicles within the ovaries. This increased the possibility of hyperestrogenism due to ovarian cysts. Serum estrogen assay indicated elevated estrogen concentration. Ovariohystorectomy was performed and tissue samples of uterus, ovaries, and skin biopsies were submitted for histopathological examination. In histological examination, the polycystic ovary was characterized by multiple follicular cysts. Results of histopathological findings in skin biopsies were similar to that reported with hyperestrogenism. In view of information achieved from the presented case, hyperestrogenism should be included in the differential diagnosis for dogs with clinical manifestation of symmetrical alopecia.