A 13.5 year old intact female Chihuahua presented for removal of a 2.7x2.4cm mammary mass that had been slowly growing from the right inguinal mammary gland for three years and had become ulcerated several days prior to presentation. A small BB-like nodule was also felt in her left caudal abdominal mammary gland. An ovariohysterectomy was performed, followed by a right inguinal/caudal abdominal mastectomy and left caudal abdominal lumpectomy. The pathology report revealed that the large mammary mass was a benign mixed adenoma, the uterus exhibited neutrophilic endometritis with hemorrhage and cystic endometrial hyperplasia, and bilateral ovotestes were present. The patient healed without complication and, at last check about six months after surgery, had returned to normal function and was doing quite well.