Background: Aspergillosis is a defiance in avian medicine, however between of Aspergillus species, 3 are the most frequently observed (A. flavus, A. fumigatus and A. niger). Psittaciformes present medical conditions related to the 3 species, however A. fumigatus is the most observed. The defiance of the diagnosis is related to fungus characteristics (they are saprophytic in healthy birds), the clinical signs and lesions, which are common to various respiratory diseases, and the difficulty to access specific diagnostic methods. Thus, we report a case of aspergillosis in a cockatiel, whose clinical diagnosis was confirmed by fungal culture of cloacal swab, and treatment with a fungistatic drug.Case: A female cockatiel, 2-month-old, not dewormed, presented diarrhea, sneezing and difficulty to gain weight, although eating well (extruded feed and supplementation with fruits and vegetables). At a clinical examination revealed body score (BCS) of 3 (scale 1 at 5), cloacal temperature (CT) of 40 ºC, dilated nostrils and edema in the left eye region associated to evident hyperemia. Due to it has lived with another animal, was inferred that was hypovitaminosis A, by food dispute and/or dominance, or endoparasitosis, being prescribed vitamin A supplementation and deworming with ivermectin. The birdreturned 15 days later, showing maintenance of weight loss, BCS 2, ruffled feathers and areas suggestive of apteriolysis in both forelimbs, respiratory difficulty and pulmonary and cranial air sacs rales, in addition presented wound in the pygostyle region and ventus, occasioned by attempted attack of a dog, and aggravated by self-mutilation. Due the worsening of the clinical condition, an oral cavity and cloacal swabs were collected to bacteriological and fungal culture. As treatment was prescribed: a natural tranquilizer, seeking to control the self-mutilation; doxycycline oral suspension, to treat a probable bacterial respiratory infection; and oral itraconazole suspension, manipulated and with a dose calculated by allometric ...