An eight-year-old Thoroughbred mare was presented with acute colic symptoms. Clinicaland ultrasonographic examination revealed a suspicion of diaphragmatic hernia, which wasconfirmed during an emergency midline laparotomy performed the same day. Patients withdiaphragmatic hernia pose a challenge for the surgeon and the anesthesiologist, because of thedisturbed function of the diaphragm and the displacement of the abdominal organs into the thoraciccavity. Achieving optimal ventilation and oxygenation without causing damage to the lungsis not simple. In this case, assisted-controlled, intermittent positive pressure ventilation with alow tidal volume, low pressure and relatively high respiratory rate was applied. Alongside thedifficulties during ventilation, the patient was cardiovascularly compromised. Due to the extentand position of the hernia, euthanasia was performed after obtaining the owner’s consent duringsurgery.