OBJECTIVE To determine the incidence of chyloabdomen diagnosis in cats and dogs and characterize and compare between species the corresponding clinical signs, clinicopathologic test results, and outcomes. DESIGN Retrospective case series. ANIMALS 36 cats and 17 dogs in which chyloabdomen was diagnosed at a veterinary teaching hospital between 1984 and 2014. PROCEDURES Medical records were reviewed, and data retrieved included patient signalment; clinical signs at initial evaluation; results of physical examination, diagnostic tests, and imaging studies; and outcomes. Survival analyses, descriptive statistics, and comparisons between species were completed. RESULTS The incidence of chyloabdomen at the veterinary teaching hospital during the study period was 2.0 cases/100,000 admissions for cats and 2.8 cases/100,000 admissions for dogs. The mean age at diagnosis of chyloabdomen in cats was 11.3 years, compared with 6.9 years in dogs. The most common clinical signs in dogs and cats combined were lethargy (39/51 [76%]) and anorexia (37/51 [73%]), but fewer (23/53 [43%]) had abdominal distention. Chylothorax was a common comorbidity (25/53 [47%]), with malignant neoplasia being the most common underlying diagnosis (24/53 [45%]). Survival analyses included 44 patients; median survival time from diagnosis of chyloabdomen was 31 days overall, 8 days for patients with malignant neoplasia, and 73 days for patients without neoplasia. CONCLUSIONS AND CLINICAL RELEVANCE There were multiple causes of chyloabdomen in dogs and cats of the study, and outcome depended on underlying cause. Because of this and the rarity of chyloabdomen, a multicenter prospective study of disease progression, treatment response, and clinical outcome for dogs and cats with chyloabdomen is needed.