A 9-year-old male German shepherd dog was referred for investigation of a two-month history of progressive straining during defecation, and intermittent hematuria. Complete series of laboratory tests performed. Hyperestrogenism was the main paraclinical finding. Based on plain and Contrast radiographic studies, a provisional diagnosis of paraprostatic cyst was made. Exploratory laparotomy was performed. Histopathologic examination of specimens obtained following the surgery confirmed an exceptional finding of bone metaplasia in sertoli cell tumor and paraprostatic cyst. Although osseous metaplasia has been reported in paraprostatic cyst, but concurrent similar metaplastic changes associated with sertoli cell tumor have not been described in veterinary literature.