In this case, vaginal leiomyosarcoma subsequent to pyometra is described in a 10-year old Labrador Retriever bitch. Bloody, malodorous discharge related to pyometra was present from the vagina for 4 months. Ovariohysterectomy recommended but the owner refused the operation. Three weeks after the first examination a rapidly growing mass and a bulge were noticed in the vagina. The dog underwent ovariohysterectomy and a biopsy was taken from the mass at the vagina during this surgery and submitted to pathology laboratory. It was diagnosed as leiomyosarcoma in histopathological and immunohistochemical examinations. After the mass extirpated surgically the recurrence was occurred in one and a half months later. The bitch’s general condition deteriorated rapidly and she died. Because of the late arrival of the patient to our clinic and in order to the request of the owner, treatment protocols could not be able to applied properly so the case was failed. The aim of this case is to transfer the surgical approaches to these kinds of reproductive pathologies to the literature. It is concluded that these kinds of pathologies should be treated immediately.