A 2-year-old intact female Cavalier King Charles Spaniel presented to the triage service at the Cornell University Hospital for Animals (CUHA) with a 5-day history of icterus, severe lethargy, anorexia, and vomiting. The patient had a history of eating 2-3 pieces of xylitol-containing chewing gum 8 days before presentation to her referring veterinarian (48 hours before the onset of her clinical signs). Multiple laboratory abnormalities referable to liver damage were observed. Hepatic lymphadenopathy was detected on abdominal ultrasound. A presumptive diagnosis of xylitol toxicosis was made based on the patient's history and laboratory findings. Supportive and hepatoprotective therapy was instituted and the patient recovered after a treatment course of several weeks. Principals of the pathogenesis, diagnosis, treatment, and prognosis of canine xylitol toxicosis are discussed.