An 11-months-old mixed Terrier male originally from Venezuela, was referred to a Veterinary Hospital with signs of depression, anorexia, vomiting and diarrhea. The illness had begun 1 month earlier. Despite antibiotic chemotherapy and vitamins, the disease progressed. Radiological exams showed involvement of the small intestine. Histopathological studies of tissue samples taken during surgical intervention revealed eosinophilic areas in the center of which, abundant eosinophils, histiocytes and giant cells were observed. Silver stained cross-sections of the small intestine showed slender sparsely septate hyphae within the necrotic areas. Attempts to isolate the etiologic agent in pure culture were fruitless. The dog died without a definitive diagnosis. Fixed tissue samples of the small intestine were later investigated using specific fluorescent antibodies for pythiosis and molecular tools. These exams indicated that the hyphae in the infected tissues belong to the straminipilan pathogen Pythium insidiosum. This is the first confirmed case of dog pythiosis in Venezuela.