Ovarian Remnant Syndrome (ORS) is a gynecopathological disorder in which eostrus and pseudopregnancy like signs are observed after ovarioectomy or ovariohysterectomy (OHE) in animals. The syndrome is generally occurred due to iatrogenic failure, in which both ovaries are not completly removed, especially ovarian cortex, in surgical operations. In this case, in a 1½ year old mix breed cat showed typical estrous signs. Cornified vaginal epithelial cells were seen in cytological examination. Eostrodiol-progesteron levels were measured as 52.3 pg/ml and 0.311 ng/ml  respectively. After operation, biopsy was performed. Papillary formations were detected in lumin of cystic structure of the remnant ovary. In immunohistochemistry, mild to moderate positive reactions were obtained from ER (eostrogen receptor), PR (progesteron receptor) and Uroplakin-10 (URO-10) in epithelial cells lining papillary extentions although mild positive reactions were obtained from Transforming Growth Factor-β1 (TGF- β1). URO-10 was also mild in epithelial cells lining follicle like structures. URO-9 did not give any positive reaction. According to the avaialable literature, this is the first study which reported ORS with particular finidngs of immunohistochemical technique.