Background: Perineal hernia is characterized by the displacement of abdominal organs to the perineal region after rupture or weakening of the pelvic diaphragm muscles. This condition is common among middle-aged and elderly unneutered male dogs. Considering the severity of the condition and its rarity among bitches, this paper reports on a case of perineal hernia caused by hydrometra in a 12-year-old pinscher bitch.Case: The patient was a 12-year-old Pinscher bitch, weighing 3 kg, suffering from anuria and constipation in the 36 h prior to treatment, without reported trauma. She was unspayed, and her last estrus had occurred approximately thirty days previously. The physical examination revealed an increase in volume in the right perineal region, increased volume in the left inguinal region, increased body temperature (39.8ºC), pale mucous membranes, tachycardia, tachypnea, abdominal pain and increased popliteal lymph nodes. The diagnosis was determined based on her medical history, clinical signs and an ultrasound scan, which revealed dilated uterine horns displaced unilaterally in the left inguinal region, with evidence of hydrometra, full urinary bladder inside the hernia sac in the right dorsolateral perineal region and right kidney pyelectasis. After evaluating the animal’s physical condition, surgery was recommended, involving ovariohysterectomy associated with inguinal and perineal herniorrhaphy.Discussion: Perineal hernia, a common condition in male dogs, is characterized by the displacement of organs towards the perineal region. However, in this case, this condition occurred in female dog. Unlike males, the main causes of perineal hernia in females are trauma, chronic coughing related to heart disease, bronchitis, and tracheal collapse. Increased intra-abdominal pressure associated with a weak pelvic diaphragm predisposes for herniation of abdominal contents, such as occurred through hydrometra. In this case, other factors that could pertain to the etiology of perineal hernia were excluded, given the absence of trauma or secondary diseases. The diagnosis was made based on a physical examination and ultrasound scan. Pre-surgical biochemical blood tests were also performed. The chosen treatment was ovariohysterectomy followed by inguinal and perineal herniorrhaphy. The traditional surgical procedure to reduce the perineal hernia was employed, using approximation sutures due to the easy apposition of wound edges. The structures and soft tissues involved showed no changes in color or texture, thus obviating the need for more elaborate techniques, which are employed in the case of relapse or muscle atrophy. The patient showed clinical evolution after surgical correction, with decreased perineal volume and recovery of urinary function (normuria). The patient was discharged after 72 h, and six months after the surgical procedure, she presented no clinical alteration, according to information provided in a telephone call by her owner. It is believed that the increase in volume caused by the presence of hydrometra was the determining factor for the development of inguinal and perineal hernias. It is suggested that alterations causing uterine enlargement be investigated in order to include perineal hernia in female dogs as a differential diagnostic tool.